Hybrid gradient-interference hardcoatings

ABSTRACT

Durable and scratch resistant articles including low-reflectance optical coating with gradient portion. In some embodiments, an article comprises: a substrate comprising a first major surface; and an optical coating disposed over the first major surface. The optical coating comprises: a second major surface; a thickness; and a first gradient portion. A refractive index of the optical coating varies along a thickness of the optical coating. The difference between the maximum refractive index of the first gradient portion and the minimum refractive index of the first gradient portion is 0.05 or greater. The absolute value of the slope of the refractive index of the first gradient portion is 0.1/nm or less everywhere along the thickness of the first gradient portion. The article exhibits a single side photopic average light reflectance of 3% or less, and a maximum hardness from 10 GPa to 30 GPa.

CLAIM OF PRIORITY

This application is a continuation application of and claims priority toU.S. patent application Ser. No. 16/643,339, filed on Feb. 28, 2020,still pending, which claims the benefit of priority under 35 U.S.C. §371 to International Patent Application No. PCT/US2018/048977, filedAug. 30, 2018, which claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Ser. No. 62/552,618 filed on Aug.31, 2017, the content of which is relied upon and incorporated herein byreference in its entirety.

BACKGROUND

The disclosure relates to durable and scratch resistant articles andmethods for making the same, and more particularly to articles with anoptical coating exhibiting abrasion resistance and scratch resistance.The optical coatings have a gradient portion, yet nevertheless exhibitoptical characteristics of multi-layer interference stacks.

Known multi-layer interference stacks are susceptible to wear orabrasion. Such abrasion can compromise any optical performanceimprovements achieved by the multi-layer interference stack. Forexample, optical filters are often made from multilayer coatings havingdiffering refractive indices and made from optically transparentdielectric material (e.g., oxides, nitrides, and fluorides). Most of thetypical oxides used for such optical filters are wide band-gapmaterials, which do not have the requisite mechanical properties, suchas hardness, for use in mobile devices, architectural articles,transportation articles or appliance articles. Nitrides and diamond-likecoatings may exhibit high hardness values but such materials do notexhibit the transmittance needed for such applications.

Abrasion damage can include reciprocating sliding contact from counterface objects (e.g., fingers). In addition, abrasion damage can generateheat, which can degrade chemical bonds in the film materials and causeflaking and other types of damage to the cover glass. Since abrasiondamage is often experienced over a longer term than the single eventsthat cause scratches, the coating materials experiencing abrasion damagecan also oxidize, which further degrades the durability of the coating.

Known multi-layer interference stacks are also susceptible to scratchdamage and, often, even more susceptible to scratch damage than theunderlying substrates on which such coatings are disposed. In someinstances, a significant portion of such scratch damage includesmicroductile scratches, which typically include a single groove in amaterial having extended length and with depths in the range from about100 nm to about 500 nm. Microductile scratches may be accompanied byother types of visible damage, such as sub-surface cracking, frictivecracking, chipping and/or wear. Evidence suggests that a majority ofsuch scratches and other visible damage is caused by sharp contact thatoccurs in a single contact event. Once a significant scratch appears,the appearance of the article is degraded since the scratch causes anincrease in light scattering, which may cause significant reduction inoptical properties. Single event scratch damage can be contrasted withabrasion damage. Single event scratch damage is not caused by multiplecontact events, such as reciprocating sliding contact from hard counterface objects (e.g., sand, gravel and sandpaper), nor does it typicallygenerate heat, which can degrade chemical bonds in the film materialsand cause flaking and other types of damage. In addition, single eventscratching typically does not cause oxidization or involve the sameconditions that cause abrasion damage and therefore, the solutions oftenutilized to prevent abrasion damage may not also prevent scratches.Moreover, known scratch and abrasion damage solutions often compromisethe optical properties.

In multi-layer interference stacks having sharp interfaces between themultiple layers of the stack, such interfaces may be a weak point in theability of the stack to resist mechanical damage.

Accordingly, there is a need for new optical coatings, and methods fortheir manufacture, which are abrasion resistant, scratch resistant andhave improved optical performance, and have improved mechanicalperformance relative to multi-layer interference stacks.

SUMMARY

The present disclosure describes embodiments directed to durable andscratch resistant articles that include a low-reflectance opticalcoating that includes a gradient portion.

In some embodiments, an article comprises: a substrate comprising afirst major surface; and an optical coating disposed over the firstmajor surface. The optical coating comprises: a second major surfaceopposite the first major surface; a thickness in a direction normal tothe second major surface; and a first gradient portion. A refractiveindex of the optical coating varies along a thickness of the opticalcoating between the first major surface and the second major surface.The difference between the maximum refractive index of the firstgradient portion and the minimum refractive index of the first gradientportion is 0.05 or greater. The absolute value of the slope of therefractive index of the first gradient portion is 0.1/nm or lesseverywhere along the thickness of the first gradient portion. Thearticle exhibits a single side photopic average light reflectance of 3%or less, measured at the second major surface. The article also exhibitsa maximum hardness in the range from about 10 GPa to about 30 GPa,wherein maximum hardness is measured on the second major surface byindenting the second major surface with a Berkovich indenter to form anindent comprising an indentation depth of about 100 nm or more from thesurface of the second major surface. Refractive index “slope” ismeasured along the thickness direction over a refractive index change of0.04.

In some embodiments, any of the embodiments described herein may have adifference between the maximum refractive index of the first gradientportion and the minimum refractive index of the first gradient portionthat is 0.1 or greater.

In some embodiments, for any of the embodiments described herein, thedifference between the maximum refractive index of the first gradientportion and the minimum refractive index of the first gradient portionis 0.3 or greater.

In some embodiments, for any of the embodiments described herein, thearticle exhibits a photopic average transmittance of 80% or more,measured at the second major surface.

In some embodiments, for any of the embodiments described herein,everywhere along the thickness of the first gradient portion, theabsolute value of the slope of the refractive index of the opticalcoating is 0.02/nm or less, or 0.012/nm or less.

In some embodiments, for any of the embodiments described herein,everywhere along the thickness of the first gradient portion, theabsolute value of the slope of the refractive index of the opticalcoating is 0.001/nm or greater, or 0.005/nm or greater.

In some embodiments, for any of the embodiments described herein, theoptical coating further comprises a high hardness portion. The thicknessof the high hardness portion is 200 nm or more, or 1000 nm or more. Theaverage index of refraction in the high hardness portion is 1.6 or more.The maximum hardness of the high hardness portion is 10 GPa or more,wherein maximum hardness is measured by indenting the thick highhardness portion with a Berkovich indenter to form an indent comprisingan indentation depth of about 100 nm or more.

In some embodiments, for any of the embodiments described herein, for95% or more of the thickness of the high hardness portion, thedifference between the maximum refractive index of the high hardnessportion and the minimum refractive index of the high hardness portion is0.05 or less.

In some embodiments, for any of the embodiments described herein,everywhere along the thickness of the high hardness portion, thedifference between the maximum refractive index of the high hardnessportion and the minimum refractive index of the high hardness portion is0.05 or less.

In some embodiments, for any of the embodiments described herein, in theembodiments of any of the paragraphs in the summary section, the opticalcoating comprises, in order, along the direction of the thickness fromthe second major surface toward the first major surface: the firstgradient portion; and the high hardness portion in contact with thefirst gradient portion. Where the high hardness portion contacts thefirst gradient portion, the difference between the refractive index ofthe high hardness portion and the maximum refractive index of the firstgradient portion is 0.05 or less.

In some embodiments, for any of the embodiments described herein, theoptical coating further comprises a second gradient portion disposedbetween the high hardness portion and the substrate. The second gradientportion is in contact with the high hardness portion. The differencebetween the maximum refractive index of the second gradient portion andthe minimum refractive index of the second gradient portion is 0.05 orgreater. Everywhere along the thickness of the second gradient portion,the absolute value of the slope of the refractive index of the opticalcoating is 0.1/nm or less.

In some embodiments, for any of the embodiments described herein, therefractive index of the first gradient portion monotonically increasesalong the thickness in a direction moving away from the second majorsurface. And, the refractive index of the second gradient portionmonotonically decreases along the thickness in a direction moving awayfrom the second major surface.

In some embodiments, for any of the embodiments described herein, theoptical coating consists of the first gradient portion, the highhardness portion, and the second gradient portion, and wherein theoptical coating is in direct contact with the substrate, and wherein thesecond major surface is an outer surface.

In some embodiments, for any of the embodiments described herein, theabsolute value of the slope of the refractive index of the opticalcoating is 0.1/nm or less everywhere in the optical coating.

In some embodiments, for any of the embodiments described herein, thearticle exhibits a single side reflected color range for all viewingangles from 0 to 60 degrees, measured at the second major surface, thatcomprises all a* and all b* points comprising absolute values of 20 orless.

In some embodiments, for any of the embodiments described herein, thearticle exhibits a single side reflected color range for all viewingangles from 0 to 60 degrees, measured at the second major surface, thatcomprises all a* and all b* points comprising absolute values of 8 orless.

In some embodiments, for any of the embodiments described herein, thearticles exhibit a transmitted color range for all viewing angles from 0to 60 degrees, measured at the second major surface, that comprises alla* and all b* points comprising absolute values of 2 or less, or 1 orless.

In some embodiments, for any of the embodiments described herein, thearticle comprises a single side average photopic light reflectance of 2%or less, 1% or less, or 0.8% or less, measured at the second majorsurface.

In some embodiments, for any of the embodiments described herein, thearticle comprises a photopic average transmittance of 90% or more.

In some embodiments, for any of the embodiments described herein, theoptical coating is disposed directly on the first major surface of thesubstrate.

In some embodiments, for any of the embodiments described herein, thearticle exhibits an average transmittance or average reflectancecomprising an average oscillation amplitude of 10 percentage points orless, over the optical wavelength regime.

In some embodiments, for any of the embodiments described herein, theoptical coating comprises a thickness in the range from about 0.5 μm toabout 3 μm.

In some embodiments, for any of the embodiments described herein, thecumulative thickness of any parts of the optical coating between thehigh hardness portion and the second major surface comprising a RI of1.6 or less is 200 nm or less.

In some embodiments, for any of the embodiments described herein, thearticle comprises a maximum hardness in the range from about 12 GPa toabout 30 Gpa, or about 16 Gpa to about 30 Gpa, wherein maximum hardnessis measured on the second major surface by indenting the second majorsurface with a Berkovich indenter to form an indent comprising anindentation depth of about 100 nm or more from the surface of the secondmajor surface.

In some embodiments, for any of the embodiments described herein, theoptical coating comprises a compositional gradient, the compositionalgradient comprising at least two of Si, Al, N, and O.

In some embodiments, for any of the embodiments described herein, theoptical coating comprises a gradient selected from at least one of aporosity gradient, a density gradient and an elastic modulus gradient.

In some embodiments, for any of the embodiments described herein, thearticle further comprises a first optional layer in contact with thefirst major surface, and a second optional layer in contact with thesecond major surface.

In some embodiments, for any of the embodiments described herein, thearticle is a sunglass lens.

In some embodiments, for any of the embodiments described herein, thearticle is a scratch resistant mirror.

In some embodiments, for any of the embodiments described herein, thearticle is a lens incorporated into glasses.

In some embodiments, for any of the embodiments described herein, thearticle is a portion of a housing or cover substrate of a consumerelectronic product, the consumer electronic product comprising: ahousing having a front surface, a back surface and side surfaces;electrical components provided at least partially within the housing,the electrical components including at least a controller, a memory, anda display, the display being provided at or adjacent the front surfaceof the housing; and a cover substrate disposed over the display.

In some embodiments, for any of the embodiments described herein, amethod of forming an article comprises: obtaining a substrate comprisinga first major surface and comprising an amorphous substrate or acrystalline substrate; disposing an optical coating on the first majorsurface, the optical coating comprising a second major surface oppositethe first major surface and a thickness in a direction normal to thesecond major surface; and creating a refractive index gradient along atleast a first gradient portion of the thickness of the optical coating.A refractive index of the optical coating varies along a thickness ofthe optical coating between the first major surface and the second majorsurface. The difference between the maximum refractive index of thefirst gradient portion and the minimum refractive index of the firstgradient portion is 0.05 or greater. The absolute value of the slope ofthe refractive index of the first gradient portion is 0.1/nm or lesseverywhere along the thickness of the first gradient portion. Thearticle exhibits a single side photopic average light reflectance of 3%or less, measured at the second major surface. The article also exhibitsa maximum hardness in the range from about 10 GPa to about 30 GPa,wherein maximum hardness is measured on the second major surface byindenting the second major surface with a Berkovich indenter to form anindent comprising an indentation depth of about 100 nm or more from thesurface of the second major surface. Slope is measured along thethickness over a refractive index change of 0.04.

In some embodiments, for any of the embodiments described herein,creating a refractive index gradient comprises varying along thethickness of the optical coating at least one of the composition and theporosity of the optical coating.

In some embodiments, for any of the embodiments described herein, theoptical coating is disposed on the first major surface by a physicalvapor deposition sputter process.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from that description or recognized by practicing theembodiments as described herein, including the detailed descriptionwhich follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary, and areintended to provide an overview or framework to understanding the natureand character of the claims. The accompanying drawings are included toprovide a further understanding, and are incorporated in and constitutea part of this specification. The drawings illustrate one or moreembodiment(s), and together with the description serve to explainprinciples and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an article, according to one or moreembodiments;

FIG. 2 is a side view of an article, according to one or moreembodiments;

FIG. 3 is a side view of an article, according to one or moreembodiments;

FIG. 4 is a side view of an article, according to one or moreembodiments;

FIG. 5 is a side view of an article, according to one or moreembodiments;

FIG. 6 is a side view of an article, according to one or moreembodiments;

FIG. 7 shows a coating design for Comparative Example 1;

FIG. 8 shows a coating design for Comparative Example 1;

FIG. 9 shows reflectance spectra for Comparative Example 1;

FIG. 10 shows transmittance spectra for Comparative Example 1;

FIG. 11 shows a plot of surface reflected D65 color vs. angle forComparative Example 1;

FIG. 12 shows a coating design for Comparative Example 2;

FIG. 13 shows a coating design for Comparative Example 2;

FIG. 14 shows reflectance spectra for Comparative Example 2;

FIG. 15 shows transmittance spectra for Comparative Example 2;

FIG. 16 shows a plot of surface reflected D65 color vs. angle forComparative Example 2;

FIG. 17 shows a coating design for Example 1;

FIG. 18 shows a coating design for Example 1;

FIG. 19 shows reflectance spectra for Example 1;

FIG. 20 shows transmittance spectra for Example 1;

FIG. 21 shows a plot of surface reflected D65 color vs. angle forExample 1;

FIG. 22 shows a coating design for Example 2;

FIG. 23 shows a coating design for Example 2;

FIG. 24 shows reflectance spectra for Example 2;

FIG. 25 shows transmittance spectra for Example 2;

FIG. 26 shows a plot of surface reflected D65 color vs. angle forExample 2;

FIG. 27 shows a coating design for Example 3;

FIG. 28 shows a coating design for Example 3;

FIG. 29 shows reflectance spectra for Example 3;

FIG. 30 shows transmittance spectra for Example 3;

FIG. 31 shows a plot of surface reflected D65 color vs. angle forExample 3;

FIG. 32 shows a coating design for Example 4;

FIG. 33 shows a coating design for Example 4;

FIG. 34 shows reflectance spectra for Example 4;

FIG. 35 shows transmittance spectra for Example 4;

FIG. 36 shows a plot of surface reflected D65 color vs. angle forExample 4;

FIG. 37 shows a coating design for Example 5;

FIG. 38 shows a coating design for Example 5;

FIG. 39 shows reflectance spectra for Example 5;

FIG. 40 shows transmittance spectra for Example 5;

FIG. 41 shows a plot of surface reflected D65 color vs. angle forExample 5;

FIG. 42 shows reflectance spectra for Example 5A;

FIG. 43 shows transmittance spectra for Example 5A;

FIG. 44 shows a plot of surface reflected D65 color vs. angle forExample 5A;

FIG. 45 shows an article (eyeglass lenses) according to one or moreembodiments;

FIG. 46 shows an article (cover substrate for smart phone) according toone or more embodiments;

FIG. 47 shows an article (cover substrate for smart phone) according toone or more embodiments.

FIG. 48 shows the composition of the hardcoat of Example 6.

FIG. 49 shows a refractive index profile for the hardcoat of Example 6.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying drawings.

For some applications, specific optical properties including lowreflectance and optionally high transmittance may be desired in ahardcoating that also provides high hardness and scratch resistance.These applications may include eyeglasses, interior (eye-facing) side ofsunglasses, RF transparent backings or housings of smartphones andsimilar devices, smartphone covers, smartwatches, heads-up displaysystems, automotive windows, mirrors, display covers, touch screens, anddisplay surfaces, architectural glass and surfaces, and otherdecorative, optical, display, or protective applications.

Existing hardcoatings include both “discrete layer” multilayer designsemploying optical interference effects, as well as “gradient” designsthat employ a gradual change in refractive index. The previous discretelayer designs are typically characterized by abrupt changes inrefractive index across an interface, such as a change in refractiveindex of 0.2 or more, and in some cases 0.4 or more, across an interfaceor transition zone that is less than 2 nm, less than 1 nm, or even lessthan 0.5 nm in thickness.

Discrete layers may be more prone to certain mechanical failure modessuch as delamination, chipping, or flaking of layers due to low adhesionenergy, stresses, or atomic/molecular bond disruption between dissimilarmaterials across abrupt interfaces. Improved mechanical performancelevels have been observed under some test conditions for “gradient”films that employ gradual changes in composition (resulting in gradualchanges in refractive index). Compositional grading is believe toimprove cohesion and adhesion with the coating layer structure, leadingto improved scratch and damage resistance under some conditions.However, historically the gradient films that have been explored havebeen limited to a “bulk-like” reflectivity behavior (e.g ˜4% reflectancefor a single surface having a terminal refractive index of approximately1.45-1.55), or, when targeting reflectance levels <4%, gradientsincorporating air or porosity at the user surface have been used whichtypically lead to low scratch and damage resistance. Sub-wavelengthfeatures and interference effects normally associated with discretelayers, together with dense (non-porous) material layers, are typicallyneeded to achieve reflectance well below 4% for materials systems havinga lowest index of about 1.45 (e.g. SiO₂) being used in air.

Gradient Portions

In some embodiments, a gradient approach, optionally combined with aninterference layer approach, is used to create optical hardcoats. It isbelieved that the presence of one or more gradient portions can provideenhanced scratch and damage resistance under some conditions. In somepreferred embodiments, the materials forming the gradient portions (andoptionally, all portions of the optical coating) are fully dense, thatis they are non-porous or have a porosity or void volume that is lessthan 10%, less than 5%, or even less than 1% of the total volume of saidportions.

The refractive index of the materials described herein typicallycorrelates with mechanical properties of the materials, such as thehardness of the materials. So, an abrupt change in refractive indexmeans an abrupt change in hardness, and may also result in an abruptchange in stress, thermal expansion, atomic bond arrangement, and otherfactors which can affect mechanical performance. It is believed that anabrupt interface between two materials having a significantly differentrefractive index may be a weak point in the ability of an opticalcoating to resist mechanical damage. But, multi-layer interferencestacks rely on such abrupt changes to obtain desired optical properties.

In contrast to abrupt interfaces, a compositionally graded interface or“gradient portion” may be used to transition between differentrefractive indices. A gradient portion is believed to impart mechanicalrobustness, including scratch and damage resistance, when compared tothe alternative of an abrupt interface. A gradient portion ischaracterized by gradual changes in refractive index. For example, someor all of the refractive index transitions in the coating layerstructure may be characterized by an absolute (positive or negative)value of refractive index ‘slope’ of 0.1/nm or less (meaning less than0.1 refractive index change per nm of coating thickness), 0.05/nm orless (or less than about 0.5 per 10 nm), 0.02/nm or less (or less than0.2 per 10 nm), 0.016/nm or less, 0.012/nm or less, or even 0.01/nm orless (less than about 0.1 per 10 nm).

In some embodiments, the refractive index slope of a gradient portion is0.001 or more, 0.002 or more, or 0.005 or more.

As used herein, a refractive index “slope” may be used to describe howquickly refractive index changes as a function of position along thethickness of a film. Refractive index slope may be calculated bydividing a change in refractive index by the distance over which thatchange occurs. In an optical coating, refractive index is typicallyconstant in directions perpendicular to the direction of the coatingthickness, and the refractive index slope is measured relative todistance changes in the direction of the coating thickness, e.g.,thickness direction 126 of FIG. 1 .

A refractive index gradient may be implemented as a continuous change inrefractive index, or as a series of small steps in refractive index. Forsufficiently small step sizes, the optical and mechanical properties areexpected to be the same as those of a smooth gradient having no steps inrefractive index. But, a small step in refractive index may have alocally high refractive index slope, if the slope is measured over asufficiently small distance interval that includes a refractive indexstep, while excluding much of the distance between steps. To avoid suchanomalies from locally measuring slope over a small distance interval atthe exact position of a small step in refractive index, refractive indexslopes as described herein are measured and calculated over a discreterefractive index interval. Unless otherwise specified, the refractiveindex slopes discussed herein are measured and calculated over arefractive index interval of 0.04. In other words, the refractive indexslope is 0.04 divided by the distance over which the refractive indexchanges by 0.04. This methodology causes the distance between steps inrefractive index to be considered when calculating a refractive indexslope where the step sizes are 0.04 or less. In some embodiments, therefractive index interval over which a refractive index slope iscalculated may be 0.02, 0.03, 0.04, 0.05 or 0.06.

Where the refractive index slope is zero or near zero over a relativelylarge distance, the methodology for calculating refractive index slopedescribed above may not work, because there is no refractive indexinterval of 0.04. So, where there is no refractive index interval of0.04 over a distance of 100 nm or greater, the refractive index slopemay be calculated over a distance interval of 100 nm. In other words,the refractive index slope in this case is the change in refractiveindex (that is less than 0.04) that occurs over 100 nm, divided by 100nm.

A gradient portion may have a refractive index that increases,decreases, or oscillates across the thickness of the gradient portion asa function of distance from the substrate. Such an increase or decreasein refractive index may be monotonic.

In some embodiments, in order for the gradient portion to have asignificant effect on the optical properties of an article, thedifference between the maximum refractive index of the first gradientportion and the minimum refractive index of the first gradient portionshould be 0.05 or greater, 0.1 or greater, 0.3 or greater, or 0.4 orgreater. In some embodiments, the endpoints of a monotonic change inrefractive index forming a single gradient portion or multiple gradientportions may comprise at least one refractive index endpoint above 1.65,above 1.7, above 1.8, or even above 1.9, with another refractive indexendpoint below 1.6, below 1.55, or even below 1.5.

Thick High Hardness Portion

In some embodiments, an optical coating comprises a thick high hardnessportion in addition to a gradient portion. In these cases, the scratchresistance may be enhanced by the thick (e.g. 200 nm-5000 nm thick) highhardness portion. In some embodiments, the thickness of soft materialabove the thick high hardness portion is limited. For example, 300 nm orless, 200 nm or less or even 100 nm or less of lower-hardness orlow-refractive-index material (e.g. SiO₂) may be above the thick hardlayer (i.e. disposed on the outside-facing or user surface) of thehardcoated article. The amount of lower-hardness or low-refractive-indexmaterial above the thick hard layer may be zero, or may be 1 nm or more.

So long as the refractive index and hardness criteria described hereinare met, the thick high hardness portion need not be truly a singlematerial or a single layer. For example, the thick hard layer cancomprise many thin layers or nanolayers, such as in a “superlattice”structure, or other hard layer structures comprising multiple materials,compositions, or structural layers or gradients. Without being limitedby theory, in a superlattice structure, a stack of sufficiently thinlayers of different materials may result in a unique microstructure suchthat the superlattice structure has optical and mechanical propertiessimilar to a thick layer of a single material, with a hardness exceedingthat of any of the materials in the individual thin layers. Exemplarystructures are disclosed in WO2016/138195, which is incorporated byreference in its entirety.

The thick high hardness portion may have an average refractive index of1.6 or more, 1.7 or more, or 1.8 or more. These refractive indicesgenerally correspond to high hardness material selections. The highhardness portion may have an indentation hardness of 10 GPa or greater,12 GPa or greater, 14 GPa or greater, GPa or greater, 18 GPa or greater,or 20 GPa or greater, or between 10 and 30 GPa.

The thick high hardness portion may have a physical thickness of 200 nm,300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1200nm, 1400 nm, 1600 nm, 1800 nm, 2000 nm, 2500 nm, 3000 nm, 3500 nm, 4000nm, 4500 nm, 5000 nm, 10000 nm, and all ranges and sub-rangestherebetween.

The thick high hardness layer may have a maximum hardness, as measuredby the Berkovich Indenter Hardness Test, of about 10 GPa or greater,about 12 GPa or greater, about 15 GPa or greater, about 18 GPa orgreater, or about 20 GPa or greater. The thick high hardness portion maybe deposited as a single layer in order to characterize hardness.

In some embodiments, a thin soft layer may be incorporated into thethick high hardness portion. For example, 95% or more of the thicknessof the high hardness portion, the maximum refractive index and theminimum refractive index may be within 0.05 of each other. But, for 5%of the thickness of the high hardness portion may have a lowerrefractive index. In this case, this lower refractive index (andcorrespondingly softer material) may be buried sufficiently deep in theoptical coating that its impact on overall structural properties is nottoo great. But, it is preferred to avoid such a softer material in thethick high hardness portion. For example, the maximum refractive indexand the minimum refractive index may be within 0.05 of each othereverywhere within the thick high hardness portion.

In some embodiments, the thick high hardness portion may have arelatively constant (and high) refractive index. For example, themaximum refractive index and the minimum refractive index may be within0.05 of each other for 95% of the thickness of the thick high hardnessportion, or everywhere within the thick high hardness portion. In someembodiments, the refractive index in the thick high hardness portion mayhave a gradient, and that the maximum refractive index and the minimumrefractive index may differ by more than 0.05 in the thick high hardnessportion.

Limited or No Abrupt Interfaces in the Hardcoat

In some embodiments, in addition to incorporating a gradient portion anda high hardness portion, the optical coating has limited or no abruptinterfaces. An abrupt interface occurs where there is an abrupt changein refractive index over a short distance. It is believed that suchabrupt interfaces may be a weak point that may degrade mechanicalproperties. Abrupt interfaces may be avoided, for example, by usinggradient portions and thick high hardness portions in the opticalcoating instead of multi-layer interference stacks, and by indexmatching at the boundary between different portions in the opticalcoating.

In some embodiments, abrupt interfaces may be present, but any abruptinterfaces are buried beneath a thick high hardness portion. A gradientportion may be present above the thick high hardness portion. It isbelieved that the thick high hardness portion protects any underlyinglayers from mechanical damage, such that the presence of abruptinterfaces beneath the thick high hardness portion may have little or nodeleterious effects on mechanical properties.

In some embodiments, abrupt interfaces are avoided altogether in theoptical coating. The optical coating consists of only gradient portions,thick high hardness portions, and optionally thin (e.g. <200 nm)low-refractive index portions having constant index. It is believed thatthe lack of abrupt interfaces enhances mechanical properties. Forexample, everywhere in the optical coating, the absolute value of theslope of the refractive index of the optical coating may be 0.1/nm orless, 0.05/nm or less, 0.02/nm or less, 0.016/nm or less, 0.012/nm orless, or even 0.01/nm or less.

In some embodiments, abrupt interfaces are avoided at interfaces betweengradient portions and/or thick high hardness portions. For example, thedifference in refractive index at such an interface when moving acrossthe interface from one portion to another may be 0.05 or less, 0.04 orless, 0.03 or less, 0.02 or less, 0.01 or less, or 0.005 or less.

Low Reflectance

In some embodiments, an optical hardcoat using a gradient approachnevertheless employs optical interference effects to generateanti-reflective surfaces having a reflectivity below the bulkreflectivity of the materials forming the article. A single-surfacereflectivity well below 4% in the visible range can be achieved, even inthe absence of abrupt interfaces in the optical coating.

Specifically, one or more surfaces of the hardcoated articles or one ormore interfaces of the hardcoating may have a reflectance of 4% or less,3% or less, 2% or less, 1.5% or less, 1% or less, 0.8% or less, 0.75% orless, 0.7% or less, 0.6% or less, 0.5% or less, 0.45% or less, or even0.4% or less. These reflectance values may represent the single-surfacearticle reflectance at 550 nm wavelength, a reflectance average from500-600 nm wavelength, a reflectance average from 450-650 nm, areflectance average from 420-680 nm, a reflectance average from 400-700nm, or a photopic average reflectance. Unless otherwise specified,reflectances described herein are photopic average reflectances.

Surprisingly, these reflectance may be achieved using hardcoats thatincorporate a gradient portion. More surprisingly, these reflectance maybe achieved using hardcoats that do not have any abrupt interfaces,i.e., where the entire hardcoat is one or more gradient portions, thickhigh hardness portions, or thin (e.g. <200 nm) low-refractive indexportions having full density and low or no porosity. These lowreflectance values are surprising because, for hardcoatings, multi-layerinterference stacks having abrupt interfaces are typically used togenerate reflectances in this range.

As used herein, the term “transmittance” is defined as the percentage ofincident optical power within a given wavelength range transmittedthrough a material (e.g., the article, the substrate or the optical filmor portions thereof). The term “reflectance” is similarly defined as thepercentage of incident optical power within a given wavelength rangethat is reflected from a material (e.g., the article, the substrate, orthe optical film or portions thereof). Transmittance and reflectance aremeasured using a specific linewidth. In one or more embodiments, thespectral resolution of the characterization of the transmittance andreflectance is less than 5 nm or 0.02 eV. Unless otherwise specified,reflectance and transmittance are measured at a near-normal incidence.

High Transmittance

In some embodiments, an optical hardcoat using a gradient approachnevertheless employs optical interference effects to generate a lowreflectance, high transmittance article. The single surface reflectancedescribed above may be obtained along with high photopic averagetransmittance, even in the absence of abrupt interfaces in the opticalcoating.

Specifically, the hardcoated articles may have a total articletransmittance of 80% or more, 85% or more, 90% or more, 92% or more, 94%or more, or even 95% or more, said values being applicable to one ormore of the optical wavelength ranges specified for reflectance above.Unless otherwise specified, transmittances described herein are photopicaverage transmittances.

Surprisingly, these transmittances and reflectances may be achievedusing hardcoats that incorporate a gradient portion. More surprisingly,these transmittances and reflectance may be achieved using hardcoatsthat do not have any abrupt interfaces, i.e., where the entire hardcoatis one or more gradient portions, thick high hardness portions, or thinlow-refractive index portions. These high transmittance values incombination with high hardness and/or scratch resistance are surprisingbecause multi-layer interference stacks having abrupt interfaces aretypically used to generate such a combination.

Overall Optical Coating Thickness

The physical thickness of optical coating 120 may be in the range fromabout 0.1 μm to about 5 μm. In some instances, the physical thickness ofthe optical coating 120 may be in the range from about 0.01 μm to about0.9 μm, from about 0.01 μm to about 0.8 μm, from about 0.01 μm to about0.7 μm, from about 0.01 μm to about 0.6 μm, from about 0.01 μm to about0.5 μm, from about 0.01 μm to about 0.4 μm, from about 0.01 to about 0.3μm, from about 0.01 μm to about 0.2 μm, from about 0.01 μm to about 0.1μm, from about 0.02 μm to about 1 μm, from about 0.03 μm to about 1 μm,from about 0.04 μm to about 1 μm, from about 0.05 μm to about 1 μm, fromabout 0.06 μm to about 1 μm, from about 0.07 μm to about 1 μm, fromabout 0.08 μm to about 1 μm, from about 0.09 μm to about 1 μm, fromabout 0.1 μm to about 1 μm, from about 0.1 μm to about 2 μm, from about0.1 μm to about 3 μm, from about 0.1 μm to about 4 μm, from about 0.1 μmto about 5 μm, from about 0.2 μm to about 1 μm, from about 0.2 μm toabout 2 μm, from about 0.2 μm to about 3 μm, from about 0.2 μm to about4 μm, from about 0.2 μm to about 5 μm, from about 0.3 μm to about 5 μm,from about 0.4 μm to about 5 μm, from about 0.5 μm to about 10 μm, fromabout 0.6 μm to about 3 μm, from about 0.7 μm to about 2 μm, from about0.8 μm to about 1 μm, or from about 0.9 μm to about 1 μm, and all rangesand sub-ranges therebetween. Other thicknesses may be suitable as well.

Materials and Processes for Hardcoating

In some embodiments, the coating structure may include hard oxide,nitride, or oxynitride layers, optionally in combination with metalliclayers. Preferred hardcoating materials include AlNx, SiNx, SiOxNy,AlOxNy, SiuAlvOxNy, SiO2, Al2O3, and compositional mixtures thereofhaving intermediate values of refractive index and hardness representingthe combined/mixed properties of these materials.

In some embodiments, metal mode sputtering may be used to deposit ahardcoating. In metal mode sputtering, samples are affixed to a movingsurface which sequentially passes by a metal sputtering source as stepone, and subsequently by a plasma source as step two. The plasma sourcecan contain oxygen and nitrogen. Steps one and two are repeated manytimes in order to deposit a thick film that consists of metal layersthat are reacted with oxygen or nitrogen to form hard oxide, nitride, oroxynitride layers.

During the metal mode sputtering process, when the samples are in frontof the metal source they are coated with a thin layer of metal. Thethickness of metal that is deposited during one pass in front of themetal source depends on the metal deposition metal rate and the lengthof time that the samples spend in front of the metal source. When thesamples then move to the plasma source position, the thin layer of metalis reacted with the plasma to form a thin film of metal nitride and/ormetal oxide. The extent, or completeness, of the chemical reaction toform the metal nitrides or oxides depends on the chemical activity ofreactive nitrogen and oxygen species, the chemical activity of the metalsurface, and the length of time that the samples spend in front of theplasma source.

For example, samples can be mounted on a cylindrical drum where the axisof the drum is oriented vertically. The diameter of the drum and therotation rate (sometimes measured in revolutions per minute) determinethe velocity with which the samples move over metal and plasma sources.The cylindrical drum is contained in a vacuum chamber which contains asputtering source (metal source) and an Inductively Coupled Plasma (ICP)source. The cylinder is rotated about its axis in order to move thesamples past the metal and plasma sources in a sequential and repeatingpattern.

The sputtering source rate is determined by processing parametersincluding the flows of gasses, the pressure of the chamber, the distanceseparating the samples from the magnetron sources, the powers applied tothe sputtering sources, the shape and size of the sputtering sources,and other features. The chemical activities for the plasma constituentscan be quantified via actinometry or electrical probing. Thesemeasurements can quantify the plasma densities, the electronicpotentials and the ion and electron temperature distributions. However,these can be laborious measurements, and are often not performed.Rather, the ICP plasma is often described by the coil size, the power tothe coil, and the flows of gasses to the area of the coil.

The films described herein were deposited by metal mode sputtering usinga deposition chamber that was manufactured by OptoRun (a company). Thedrum diameter was about 1650 millimeters and the rotation rate was 80rpm. The chamber pressure was about 2 millitorr. We used dual rotatablecylindrical magnetron targets having a length of about 850 millimetersand a diameter of about 180 millimeters. The sputtering surface of thetargets consisted of Silicon and/or Aluminum. The magnets of themagnetron produced a magnetic field strength of about 500 gauss at thesurface of the target. The power was applied to the magnetron pair inalternating current (AC) mode, being supplied by a Huttinger (a company)power supply operating in mid-frequency mode. During one half of an ACcycle of the mid-frequency mode, one magnetron cylinder is powered asthe cathode (negative charge) while the other magnetron cylinder ispowered as an anode (positive charge). The throw distance from themagnetron surface to the surfaces of the samples was about 100millimeters. The reactor used four planar spiral pancake coils for theICP, located at the corners of a square array. Each of the four coilsconsisted of about 2 turns of an about 12 mm diameter copper coil, andhad a diameter of about 400 millimeters. The coils were customfabricated by OptoRun (a compay).

The SiN and SiON processes that were used for the data of thisapplication used the set of conditions specified in the table below.

TABLE 1 SiN_(x) - single layer Start-up: ramp up time 60 s Magnetronpairs 2, 3, 4 Ar flow: 140 sccm each Power, magnetron pair 2 (Si) 0 kWto Si ICP power 0.5 −> 4 kW ICP flow Ar 80 sccm ICP flow O2 150 sccm ICPflow N2 0 sccm Deposition: Dep time 2600 s Magnetron paris 2, 3, 4 Arflow: 140 sccm each Power, magnetron pair 2 (Si) 9 kW to Si ICP power 4kW ICP flow Ar 80 sccm ICP flow O2 0 sccm ICP flow N2 150 sccmSiO_(x)N_(y) - single layer Start-up: ramp up time 60 s Magnetron pairs2, 3, 4 Ar flow: 140 sccm each Power, magnetron pair 2 (Si) 0 kW to SiICP power 0.5 −> 4 kW ICP flow Ar 80 sccm ICP flow O2 150 sccm ICP flowN2 0 sccm Deposition: Dep time 2600 s Magnetron paris 2, 3, 4 Ar flow:140 sccm each Power, magnetron pair 2 (Si) 9 kW to Si ICP power 4 kW ICPflow Ar 80 sccm ICP flow O2 20 sccm ICP flow N2 150 sccm

Other processes can produce SiNx and SiOxNy, where the material producedby those other processes may have the properties that are claimed inthis application. Other processes that can make SiNx and SiOxNy filmsinclude reactive sputtering, evaporative technologies such as electronbeam evaporation, Chemical Vapor Deposition (CVD), Plasma EnhancedChemical Vapor Deposition (PECVD), Atomic Layer Deposition (ALD),plating technologies such as electroplating, and wet chemical depositiontechnologies such as sol-gel.

Sputtering process conditions for high-hardness SiNx, SiOxNy, andSiuAlvOxNy were found to deliver hardness and refractive index valuessubstantially identical to high-hardness AlOxNy, further described inU.S. Pat. No. 9,335,444, which is incorporated by reference in itsentirety. These high-hardness materials are characterized by a measuredsingle-layer film hardness of >16, >18, >20, or from 16 GPa to 25 GPafor single-layer films of 500-5000 nm thickness on glass substrates(where the glass substrate has a hardness of ˜7 GPa). Thesehigh-hardness materials are also generally characterized by refractiveindex (n) values (measured at 550 nm) of about 1.85-2.1, and complexrefractive index (absorption coefficient, k) values less than about 1e−2, less than 5 e−3, less than 1 e−3, or even less than 5 e−4 asmeasured at 400 nm wavelength. K is measured at 400 nm for greatersensitivity, while n is typically reported at 550 nm. Generallyspeaking, all of these high-hardness materials can be fabricated byreactive sputtering, metal-mode reactive sputtering, and PECVD atprocess temperatures below 400 C or even below 300 C.

It has been found that “AlON,” “SiON”, and “SiAlON” based compositionsare substantially interchangeable in the optical designs disclosed here,when properly tuned to achieve the desired combinations of hardness,refractive index, film stress, and low optical absorption. A preferredthin film deposition process is reactive or metal-mode sputtering,though other processes such as PECVD are also avenues for fabricatingthe coatings of the present disclosure. For the purposes of thisdisclosure, single and multi-layer films of AlOxNy, SiOxNy, andSiuAlvOxNy may be fabricated by reactive and metal-mode sputtering, andtheir hardness and optical properties tuned to achieve the desiredranges. Suitable fabrication processes are described, for example, inU.S. Pat. No. 9,335,444, which is incorporated by reference in itsentirety. The measured optical properties of these coatings were used inthin-film design simulations to generate the modeled examples of thepresent disclosure.

The optical layers (which may be hard layers or softer layers) may alsoinclude additional materials known in the thin film art such as SiO₂,Al₂O₃, TiO₂, Nb₂O₅, Ta₂O₅, HfO₂, others known in the art, and mixtures,layered structures, and combinations thereof.

Applications

In some embodiments, applications include display covers, touchscreens,smartphone housing components such as cover elements or backings (e.g.hardcoated glass or glass ceramics), exterior of sunglasses, andscratch-resistant mirrors.

Different substrates may be used for different applications. The modeledexamples herein use Corning glass code 5318, available from CorningIncorporated, Corning, N.Y. It should be understood that alternatesubstrates can also be used as substrates for these coating designs.Non-limiting examples include clear non-absorbing glass such as Gorillaglass, or glass ceramics such as chemically strengthened black glassceramic. The first-surface reflectance and reflected color values remainsubstantially the same with these different choices of substrate (whilethe transmission values will be largely changed by the choice ofsubstrate). In the case of black glass-ceramic substrates, the totalarticle transmission can be less than 10% or less than 1%. In the caseof clear non-absorbing substrates, the transmittance will beapproximately 100-% Reflectance of coating (1^(st) surface), or 100-4-%Reflectance of coating (the latter case accounting for a 4% Reflectancefrom the rear, uncoated surface of the clear glass substrate).

Absorbing and Metal Layers

In some embodiments, hardcoating designs described herein can becombined with metallic layers or absorbing layers. Absorbing layers maybe particularly useful in sunglasses applications where it is desirableto minimize the reflectance on the user side of the coated article. Inthese cases, it may be preferable to locate absorbing material on theuser side of the hardcoating, such as an absorbing glass substratefacing the user's eyes, and the reflective or colored hardcoatings onthe external-facing surface of the article for both reflectance andscratch resistance towards the external environment. In these casesincorporating a one-sided absorbing article structure, the reflectancefrom the two sides of the article can vary due to the absorber. In thesecases, unless otherwise specified, the reflectance values quoted herewill apply to the environment-facing surface, the hardcoated surface, orthe surface having a low level of absorption between the environment andthe hardcoating/reflection layers. In some embodiments, an absorbinglayer may be located between a hardcoating and a substrate. In someembodiments, it may be desirable to exclude metals from the stack, as inthe examples described below, to maximize adhesion and scratchresistance.

Positioning of Optical Coatings on Specific Articles

In some embodiments, as both sides of eyeglasses or sunglasses can besubject to abrasion, especially during cleaning, it may be desirable toplace a scratch-resistant coating on both sides of an eyeglass orsunglasses lens. In the case of an absorbing sunglass or eyeglass lens,it will often be desirable to place a higher-reflectancescratch-resistant coating on the external surface of the sunglass lens,and a low-reflectance or anti-reflection scratch-resistant coating onthe interior (user eye facing) surface of the sunglass lens. Forexample, a coating on the exterior (front) surface of the lens may havea photopic average reflectance higher than 8%, such as those describedin WO2014182639 (examples 1 and 13). The interior (back) surface of thelens may have a hardcoating with a photopic average reflectance below2%, such as the modeled examples from this disclosure. WO2016018490 andWO2014182639 are incorporated by reference in their entireties.

In some embodiments, where a scratch-resistant coating is placed on bothsides of an eyeglass or sunglasses lens, high hardness and scratchresistance is imparted to both surfaces. In these cases it may bepreferred to place a low-reflectance coating (e.g. <4% photopic averagereflectance) on the interior surface of the sunglass and ahigh-reflecting coating (e.g. >6% photopic average reflectance on theexterior surface. In this situation, the order of elements would be 1)user's eye; 2) Low-reflectance coating; 3) absorbing glass substrate; 4)High-reflectance coating; 5) sun or ambient environment. TheLow-reflectance coating may be, for example, any of the low-reflectancecoatings of the present disclosure. The high-reflectance coating may be,for example, coatings as described in WO2014182639 (examples 1 and 13).

In an eyeglasses application, as opposed to sunglasses, it may bepreferred to utilize a low-reflectance scratch-resistant coating on bothsides of a clear (non-absorbing glass substrate). In other cases it willbe more cost-effective to use a single scratch resistant coating, mostlikely on the exterior facing surface of the eyeglasses or sunglasses.

In some embodiments, coatings described herein may also be useful inautomotive glass applications, e.g. side windows or sunroofs or lampcovers. The coatings can provide a low-reflectance scratch-resistantcoating having high scratch and weathering resistance.

In display cover and touchscreen applications, it will typically bepreferred to place the optical hardcoating on the user-facing/exposedsurface of the display or screen, though in some such applications itmay be desirable to place the coatings on both sides of a display cover,or optionally to have two different coatings on two sides of a displaycover. For example, a low-cost, low-hardness anti-reflective coating maybe placed on the back side of a display cover, which may be protectedfrom scratching due to its position, while a high-hardnessanti-reflective coating such as the embodiments of the presentdisclosure may be placed on the front, user-facing side of the displaycover.

Parameters

Parameters that may be considered and specified based on the disclosureherein include the following:

-   -   Hardness of coated article, coated surface.    -   Fraction of softer (typically lower refractive index) material        in the coating stack.    -   Total amount (thickness) of softer material in the coating        stack.    -   Total amount (thickness) of softer material on the exposed (away        from substrate) side of the thickest high hardness (high index)        layer.    -   Maximum reflectance in the visible range.    -   Average reflectance in the visible range (e.g. photopic average        reflectance.    -   Transmittance in the visible range (with or without combination        with absorbing materials or substrates).    -   Reflected color and color shift with optical angle of incidence.    -   Transmitted color and color shift with optical angle of        incidence.

Article Structure

Referring to FIG. 1 , the article 100 according to one or moreembodiments may include a substrate 110, and an optical coating 120disposed on the substrate. The substrate 110 includes opposing majorsurfaces 112, 114 and opposing minor surfaces 116, 118. The opticalcoating 120 is shown in FIG. 1 as being disposed on major surface 112;however, the optical coating 120 may be disposed on major surface 114and/or one or both of the opposing minor surfaces, in addition to orinstead of being disposed on major surface 112. The optical coating 120forms an outer surface 122. Surface 112 may also be referred to hereinas a “first major surface,” and surface 122 may be referred to herein asa “second major surface.”

As illustrated, optical coating 120 includes opposing major surfaces122, 124 parallel to opposing major surfaces 112, 114, and perpendicularto a thickness direction 126 of optical coating 120.

The thickness of the optical coating 120 may be about 1 μm or greaterwhile still providing an article that exhibits the optical performancedescribed herein. In some examples, the optical coating 120 thicknessmay be in the range from about 1 μm to about 20 μm (e.g., from about 1μm to about 10 μm, or from about 1 μm to about 5 μm). Thickness of thethin film elements (e.g., scratch-resistant layer, layers of the opticalfilm, etc.) was measured by scanning electron microscope (SEM) of across-section, by transmission electron microscope (TEM), or by opticalellipsometry (e.g., by an n & k analyzer), or by thin filmreflectometry. For multiple layer elements (e.g., layers of the opticalfilm stack), thickness measurements by SEM or TEM are preferred. Unlessotherwise specified, ellipsometry is used to measure thickness.

Article 100 may also include 1 or more optional layers 170, 180. Forexample, optional layer 170 may be an adhesion layer, a crack-mitigatinglayer, and optional layer 180 may be an easy to clean layer. Optionallayers 170 and 180 are optional, and need not be included in article100. While optional layers 170, 180 are omitted from figures other thanFIG. 1 , they may optionally be present in the embodiments of such otherfigures.

As used herein, the term “layer” may include a single layer or mayinclude one or more sub-layers. Such sub-layers may be in direct contactwith one another. The sub-layers may be formed from the same material ortwo or more different materials. In one or more alternative embodiments,such sub-layers may have intervening layers of different materialsdisposed therebetween. In one or more embodiments a layer may includeone or more contiguous and uninterrupted layers and/or one or morediscontinuous and interrupted layers (i.e., a layer having differentmaterials formed adjacent to one another). A layer or sub-layers may beformed by any known method in the art, including discrete deposition orcontinuous deposition processes. In one or more embodiments, the layermay be formed using only continuous deposition processes, or,alternatively, only discrete deposition processes.

As used herein, the term “dispose” includes coating, depositing and/orforming a material onto a surface using any known method in the art. Thedisposed material may constitute a layer, as defined herein. The phrase“disposed on” includes the instance of forming a material onto a surfacesuch that the material is in direct contact with the surface and alsoincludes the instance where the material is formed on a surface, withone or more intervening material(s) is between the disposed material andthe surface. The intervening material(s) may constitute a layer, asdefined herein.

As shown in FIG. 2 , article 200 includes an optical coating 120 whichincludes a first gradient portion 130. FIG. 2 illustrates a generalembodiment in which optical coating may or may not include additionallayers 125. Additional layers 125 may be gradient portions, thick highhardness portions, multi-layer interference stacks, or other opticalcoating components. There may be more or less additional layers 125 thanare illustrated in FIG. 2 . First gradient portion 130 may be locatedanywhere in optical coating 120, including touching one or both ofopposing major surfaces 122, 124.

As shown in FIG. 3 , article 300 includes an optical coating 120 thatincludes both a first gradient portion 130 and a thick high hardnessportion 140. As with FIG. 2 , FIG. 3 illustrates additional layers 125that may or may not be present, and that may be the same type of layersdescribed with respect to additional layers 125 of FIG. 2 . Each offirst gradient portion 130 and thick high hardness portion 140 may belocated anywhere in optical coating 120, including touching one ofopposing major surfaces 122, 124.

FIG. 4 illustrates an article 400, a specific embodiment in whichoptical coating 120 consists of thick high hardness portion 140 andfirst gradient portion 130 stacked in that order over substrate 110,without intervening layers, and without any additional layers 125 inoptical coating 120.

FIG. 5 illustrates an article 500, a specific embodiment in whichoptical coating 120 consists of second gradient portion 150, thick highhardness portion 140 and first gradient portion 130 stacked in thatorder over substrate 110, without intervening layers, and without anyadditional layers 125 in optical coating 120. In some embodiments, thestructure of FIG. 5 may have a refractive index that monotonicallyincreases along the thickness in a direction moving away from surface122 toward surface 112. And, the refractive index of the second gradientportion monotonically decreases in the same direction. As used herein,“monotonically increases” means that the refractive index goes up orremains the same as a function of distance, but does not decrease. Asused herein, “monotonically decreases” means that the refractive indexgoes down or remains the same as a function of distance, but does notincrease. Examples 1-5 are examples of the monotonic functions describedin this paragraph.

Multi-Layer Interference Stacks

In some embodiments, additional layers 125 may comprise one or moremulti-layer interference stacks. FIG. 6 illustrates an exemplary article600 that includes a multi-layer interference stack 610. In theembodiment of FIG. 6 , optical coating 120 consists of multi-layerinterference stack 610, thick high hardness portion 140 and firstgradient portion 130 stacked in that order over substrate 110. In one ormore embodiments, the multi-layer interference stack 610 may include aperiod 620 comprising two or more layers. In one or more embodiments,the two or more layers may be characterized as having differentrefractive indices from each another. In some embodiments, the period620 includes a first low RI layer 622 and a second high RI layer 624.The difference in the refractive index of the first low RI layer and thesecond high RI layer may be about 0.01 or greater, 0.05 or greater, 0.1or greater or even 0.2 or greater.

As shown in FIG. 6 , the multi-layer interference stack 610 may includea plurality of periods 620. A single period includes include a first lowRI layer 622 and a second high RI layer 624, such that when a pluralityof periods are provided, the first low RI layer 622 (designated forillustration as “L”) and the second high RI layer 624 (designated forillustration as “H”) alternate in the following sequence of layers:L/H/L/H or H/L/H/L, such that the first low RI layer and the second highRI layer appear to alternate along the physical thickness of themulti-layer interference stack 610. In the example in FIG. 6 , themulti-layer interference stack 610 includes three periods. In someembodiments, the multi-layer interference stack 610 may include up to 25periods. For example, the multi-layer interference stack 610 may includefrom about 2 to about 20 periods, from about 2 to about 15 periods, fromabout 2 to about 10 periods, from about 2 to about 12 periods, fromabout 3 to about 8 periods, from about 3 to about 6 periods.

A multi-layer interference stack may include other layers as well, suchas layers having high or low refractive indices different from those offirst low RI layer 622 and second high RI layer 624, or layers having amedium index of refraction. As used herein, the terms “low RI”, “highRI” and “medium RI” refer to the relative values for the RI to another(e.g., low RI<medium RI<high RI). In one or more embodiments, the term“low RI” when used with the first low RI layer or with the third layer,includes a range from about 1.3 to about 1.6. In one or moreembodiments, the term “high RI” when used with the second high RI layeror with the third layer, includes a range from about 1.6 to about 2.5(e.g., about 1.85 or greater). In some embodiments, the term “medium RI”when used with the third layer, includes a range from about 1.55 toabout 1.8. In some instances, the ranges for low RI, high RI and mediumRI may overlap; however, in most instances, the layers of a particularmulti-layer interference stack 610 have the general relationshipregarding RI of: low RI<medium RI<high RI.

Exemplary materials suitable for use in the multi-layer interferencestack 610 include: SiO₂, Al₂O₃, GeO₂, SiO, AlOxNy, AlN, SiN_(x),SiO_(x)N_(y), Si_(u)Al_(v)O_(x)N_(y), Ta₂O₅, Nb₂O₅, TiO₂, ZrO₂, TiN,MgO, MgF₂, BaF₂, CaF₂, SnO₂, HfO₂, Y₂O₃, MoO₃, DyF₃, YbF₃, YF₃, CeF₃,polymers, fluoropolymers, plasma-polymerized polymers, siloxanepolymers, silsesquioxanes, polyimides, fluorinated polyimides,polyetherimide, polyethersulfone, polyphenylsulfone, polycarbonate,polyethylene terephthalate, polyethylene naphthalate, acrylic polymers,urethane polymers, polymethylmethacrylate, other materials cited belowas suitable for use in a scratch-resistant layer, and other materialsknown in the art. Some examples of suitable materials for use in thefirst low RI layer include SiO₂, Al₂O₃, GeO₂, SiO, AlO_(x)N_(y),SiO_(x)N_(y), Si_(u)Al_(v)O_(x)N_(y), MgO, MgAl₂O₄, MgF₂, BaF₂, CaF₂,DyF₃, YbF₃, YF₃, and CeF₃. The nitrogen content of the materials for usein the first low RI layer may be minimized (e.g., in materials such asAl₂O₃ and MgAl₂O₄, or for example, the SiO_(x)N_(y) used to form alow-index material will typically have a lower nitrogen content than anSiO_(x)N_(y) used to form a high-index material). Some examples ofsuitable materials for use in the second high RI layer includeSi_(u)Al_(v)O_(x)N_(y), Ta₂O₅, Nb₂O₅, AlN, Si₃N₄, AlO_(x)N_(y),SiO_(x)N_(y), HfO₂, TiO₂, ZrO₂, Y₂O₃, Al₂O₃, MoO₃ and diamond-likecarbon. The oxygen content of the materials for the second high RI layerand/or the scratch-resistant layer may be minimized, especially in SiNxor AlNx materials. AlO_(x)N_(y) materials may be considered to beoxygen-doped AlNx, that is they may have an AlNx crystal structure (e.g.wurtzite) and need not have an AlON crystal structure. Exemplarypreferred AlO_(x)N_(y) high RI materials may comprise from about 0 atom% to about 20 atom % oxygen, or from about 5 atom % to about 15 atom %oxygen, while including 30 atom % to about 50 atom % nitrogen. Exemplarypreferred Si_(u)Al_(v)O_(x)N_(y) high RI materials may comprise fromabout 10 atom % to about 30 atom % or from about 15 atom % to about 25atom % silicon, from about 20 atom % to about 40 atom % or from about 25atom % to about 35 atom % aluminum, from about 0 atom % to about 20 atom% or from about 1 atom % to about 20 atom % oxygen, and from about 30atom % to about 50 atom % nitrogen. Exemplary preferred SiO_(x)N_(y)high RI materials may comprise from about 30 atom % to about 60 atom %or from about 40 atom % to about 50 atom % silicon, from about 0 atom %to about 25 atom % or from about 1 atom % to about 25 atom % or fromabout 6 atom % to about 18 atom % oxygen, and from about 30 atom % toabout 60 atom % nitrogen. Exemplary preferred SiN_(x) high RI materialsmay comprise from about 30 atom % to about 60 atom % or from about 40atom % to about 50 atom % silicon, and from about 30 atom % to about 70atom % nitrogen. The foregoing materials may be hydrogenated up to about30% by weight. The hardness of the second high RI layer and/or thescratch-resistant layer may be characterized specifically. In someembodiments, the maximum hardness of the second high RI layer and/or thescratch-resistant layer, as measured by the Berkovich Indenter HardnessTest, may be about 10 GPa or greater, about 12 GPa or greater, about 15GPa or greater, about 18 GPa or greater, or about 20 GPa or greater. Insome cases, the second high RI layer material may be deposited as asingle layer and may be characterized as a scratch resistant layer, andthis single layer may have a thickness from about 500 nm to about 2000nm for repeatable hardness determination.

The physical thickness of a multi-layer interference stack 610 may be inthe range from about 100 nm to 1000 nm. In some instances, the physicalthickness of the multi-layer interference stack 610 may 100 nm, 200 nm,300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, and allranges and sub-ranges therebetween. In some embodiments, a multi-levelinterference stack 610 positioned between a substrate 110 and a thickhigh hardness portion, as illustrated in FIG. 6 , for example,preferably has a thickness of 100 to 500 nm. In some embodiments, amulti-level interference stack positioned above substrate 110 preferablyhas a thickness of 100 to 1000 nm.

In some embodiments, any multi-layer interference stack 610 present inoptical coating 120 is positioned beneath a thick high hardness portion140, i.e., between thick high hardness portion 140 and substrate 110.Without being bound by theory, the thick high RI layer having a highhardness effectively shields the layers underneath (or between the thickRI layer and the substrate), such that the effect of mechanical weaknesscaused by abrupt interfaces in multi-layer interference stack 610 on theproperties of article 600 are reduced.

Positioning and Thickness of Soft Material

In some embodiments, the thickness of any soft material in opticalcoating 120 may be minimized and/or positioned in certain ways.

In embodiments it may be useful to quantify the amount or thickness oflow-refractive-index (also called low-index) material in the coatingdesign. Low-index materials (generally defined as having refractiveindex below about 1.6) are typically also lower-hardness materials.Without being bound by theory, the low RI material is typically also alower-hardness material, owing to the nature of atomic bonding andelectron densities that simultaneously affect refractive index andhardness. Thus it is desirable to minimize the amount of low-indexmaterial in the coating design, but some amount of low-index material istypically desired to efficiently tailor reflection and color targets.The thickness and the fraction of low-index material (which inembodiments is understood to be a lower-hardness material) is denoted inthe design descriptions in terms of absolute thickness and fraction oftotal coating thickness. It can be useful to quantify both the totalamount of low-index material in the entire coating, as well as theamount of low-index material that is above the thickest high-hardnesslayer in the coating design. The thickest high-hardness layer in thecoating design protects the layers underneath it from scratch anddamage, meaning that the low-index layers above the thickesthigh-hardness layer are most susceptible to scratch and other types ofdamage. As noted above, the thickest high-hardness layer need not be asingle monolithic material, but can form a superlattice or other layeredstructure including multiple layers or material, provided that the thickhigh-hardness layer forms or monolithic or ‘composite’ region with amaximum hardness that is higher than the maximum hardness of the entirecoating stack.

In some embodiments, the total thickness of “soft” material (e.g. SiO2or mixed materials having a refractive index below about 1.6) above athick high hardness portion is preferably limited to less than about 200nm, less than about 150 nm, less than 120 nm, or even less than 100 nm.Such minimization of soft material above a thick hard layer may resultin a high article hardness and high scratch resistance. The articlehardness may be greater than 10 GPa, greater than 12 GPa, greater than14 GPa, or greater than 16 GPa at indentation depths from 100 to 500 nm,as measured using a Berkovich nanoindentation test.

In some embodiments, the amount of low RI material in the opticalcoating may be minimized. Expressed as a fraction of physical thicknessof the optical coating 120, the low RI material may comprise less thanabout 60%, less than about 50%, less than about 40%, less than about30%, less than about 20%, less than about 10%, or less than about 5% ofthe physical thickness of the optical coating. The low RI material maycomprise more than zero % or more than 1% of the physical thickness ofthe optical coating. Alternately or additionally, the amount of low RImaterial may be quantified as the sum of the physical thicknesses of alllow RI material disposed above the thickest high RI layer in the opticalcoating (i.e. on the side opposite the substrate, the user side or theair side). Without being bound by theory, the thick high RI layer havinga high hardness effectively shields the layers underneath (or betweenthe thick RI layer and the substrate) from many or most scratches.Accordingly, the layers disposed above the thickest high RI layer mayhave an outsized effect on scratch resistance of the overall article.This is especially relevant when the thickest high RI layer has aphysical thickness that is greater than about 400 nm and has a maximumhardness greater than about 12 GPa as measured by the Berkovich IndenterHardness Test. The amount of low RI material disposed on the thickesthigh RI layer (i.e. on the side opposite the substrate, the user side orthe air side) may have a thickness less than or equal to about 300 nm,less than or equal to about 200 nm, less than or equal to about 150 nm,less than or equal to about 120 nm, less than or equal to about 110 nm,100 nm, 90 nm, 80 nm, 70 nm, 60 nm, 50 nm, 40 nm, 30 nm, 25 nm, 20 nm,15 nm, or less than or equal to about 12 nm. The amount of low RImaterial disposed on the thickest high RI layer (i.e. on the sideopposite the substrate, the user side or the air side) may have athickness greater than or equal to about 0 nm or 1 nm.

Optional Layers

Some embodiments, may include optional layers, such as optional layers170 and 180. The top-most air-side layer, such as optional layer 180,may comprise a low-friction coating, an oleophobic coating, or aneasy-to-clean coating. Exemplary low-friction layers may include asilane, a fluorosilane, or diamond-like carbon, such materials (or oneor more layers of the optical coating) may exhibit a coefficient offriction less than 0.4, less than 0.3, less than 0.2, or even less than0.1.

In one or more embodiments, optional layer 180 may include aneasy-to-clean coating. An example of a suitable an easy-to-clean coatingis described in U.S. patent application Ser. No. 13/690,904, entitled“PROCESS FOR MAKING OF GLASS ARTICLES WITH OPTICAL AND EASY-TO-CLEANCOATINGS,” filed on Nov. 30, 2012, published as US20140113083A1, whichis incorporated herein in its entirety by reference. The easy-to-cleancoating may have a thickness in the range from about 5 nm to about 50 nmand may include known materials such as fluorinated silanes. In someembodiments, the easy-to-clean coating may have a thickness in the rangefrom about 1 nm to about 40 nm, from about 1 nm to about 30 nm, fromabout 1 nm to about 25 nm, from about 1 nm to about 20 nm, from about 1nm to about 15 nm, from about 1 nm to about 10 nm, from about 5 nm toabout 50 nm, from about 10 nm to about 50 nm, from about 15 nm to about50 nm, from about 7 nm to about 20 nm, from about 7 nm to about 15 nm,from about 7 nm to about 12 nm or from about 7 nm to about 10 nm, andall ranges and sub-ranges therebetween.

Measuring Hardness

Hardness and Young's modulus values of thin film coatings and articlesas described herein are determined using widely accepted nanoindentationpractices. See: Fischer-Cripps, A. C., Critical Review of Analysis andInterpretation of Nanoindentation Test Data, Surface & CoatingsTechnology, 200, 4153-4165 (2006) (hereinafter “Fischer-Cripps”); andHay, J., Agee, P, and Herbert, E., Continuous Stiffness measurementDuring Instrumented Indentation Testing, Experimental Techniques, 34 (3)86-94 (2010) (hereinafter “Hay”). For coatings, it is typical to measurehardness and modulus as a function of indentation depth. So long as thecoating is of sufficient thickness, it is then possible to isolate theproperties of the coating from the resulting response profiles. Itshould be recognized that if the coatings are too thin (for example,less than ˜500 nm), it may not be possible to completely isolate thecoating properties as they can be influenced from the proximity of thesubstrate which may have different mechanical properties. See Hay. Themethods used to report the properties herein are representative of thecoatings themselves. The process is to measure hardness and modulusversus indentation depth out to depths approaching 1000 nm. In the caseof hard coatings on a softer glass, the response curves will revealmaximum levels of hardness and modulus at relatively small indentationdepths (less than or equal to about 200 nm). At deeper indentationdepths both hardness and modulus will gradual diminish as the responseis influenced by the softer glass substrate. In this case the coatinghardness and modulus are taken be those associated with the regionsexhibiting the maximum hardness and modulus. In the case of softcoatings on a harder glass substrate, the coating properties will beindicated by lowest hardness and modulus levels that occur at relativelysmall indentation depths. At deeper indentation depths, the hardness andmodulus will gradually increase due to the influence of the harderglass. These profiles of hardness and modulus versus depth can beobtained using either the traditional Oliver and Pharr approach (asdescribed in Fischer-Cripps) or by the more efficient continuousstiffness approach (see Hay). The elastic modulus and hardness valuesreported herein for such thin films were measured using nanoindentationmethods, as described above, with a Berkovich diamond indenter tip.

The optical coating 120 and the article 100 may be described in terms ofa hardness measured by a Berkovich Indenter Hardness Test. As usedherein, the “Berkovich Indenter Hardness Test” includes measuring thehardness of a material on a surface thereof by indenting the surfacewith a diamond Berkovich indenter. The Berkovich Indenter Hardness Testincludes indenting major surface 122 of the article or the surface ofthe optical coating 120 (or the surface of any one or more of the layersin the multi-layer interference stack) with the diamond Berkovichindenter to form an indent to an indentation depth in the range fromabout 50 nm to about 1000 nm (or the entire thickness of the multi-layerinterference stack or layer, whichever is less) and measuring themaximum hardness from this indentation along the entire indentationdepth range or a segment of this indentation depth (e.g., in the rangefrom about 100 nm to about 600 nm), generally using the methods setforth in Oliver, W. C.; Pharr, G. M. An improved technique fordetermining hardness and elastic modulus using load and displacementsensing indentation experiments. J. Mater. Res., Vol. 7, No. 6, 1992,1564-1583; and Oliver, W. C.; Pharr, G. M. Measurement of Hardness andElastic Modulus by Instrument Indentation: Advances in Understanding andRefinements to Methodology. J. Mater. Res., Vol. 19, No. 1, 2004, 3-20.As used herein, hardness refers to a maximum hardness, and not anaverage hardness. Unless otherwise specified, hardness values providedherein refer to values measured by the Berkovich Indenter Hardness Test.

Typically, in nanoindentation measurement methods (such as by using aBerkovich indenter) of a coating that is harder than the underlyingsubstrate, the measured hardness may appear to increase initially due todevelopment of the plastic zone at shallow indentation depths and thenincreases and reaches a maximum value or plateau at deeper indentationdepths. Thereafter, hardness begins to decrease at even deeperindentation depths due to the effect of the underlying substrate. Wherea substrate having an increased hardness compared to the coating isutilized, the same effect can be seen; however, the hardness increasesat deeper indentation depths due to the effect of the underlyingsubstrate.

The indentation depth range and the hardness values at certainindentation depth range(s) can be selected to identify a particularhardness response of the optical film structures and layers thereof,described herein, without the effect of the underlying substrate. Whenmeasuring hardness of the optical film structure (when disposed on asubstrate) with a Berkovich indenter, the region of permanentdeformation (plastic zone) of a material is associated with the hardnessof the material. During indentation, an elastic stress field extendswell beyond this region of permanent deformation. As indentation depthincreases, the apparent hardness and modulus are influenced by stressfield interactions with the underlying substrate. The substrateinfluence on hardness occurs at deeper indentation depths (i.e.,typically at depths greater than about 10% of the optical film structureor layer thickness). Moreover, a further complication is that thehardness response requires a certain minimum load to develop fullplasticity during the indentation process. Prior to that certain minimumload, the hardness shows a generally increasing trend.

At small indentation depths (which also may be characterized as smallloads) (e.g., up to about 50 nm), the apparent hardness of a materialappears to increase dramatically versus indentation depth. This smallindentation depth regime does not represent a true metric of hardnessbut instead, reflects the development of the aforementioned plasticzone, which is related to the finite radius of curvature of theindenter. At intermediate indentation depths, the apparent hardnessapproaches maximum levels. At deeper indentation depths, the influenceof the substrate becomes more pronounced as the indentation depthsincrease. Hardness may begin to drop dramatically once the indentationdepth exceeds about 30% of the optical film structure thickness or thelayer thickness.

In some embodiments, the optical coating 120 may exhibit a hardness ofabout 10 GPa or greater, or about 11 GPa or greater, or about 12 GPa orgreater (e.g., 14 GPa or greater, 16 GPa or greater, 18 GPa or greater,20 GPa or greater). The hardness of the optical coating 120 may be up toabout 20 GPa, 30 GPa, or 50 GPa. The article 100, including the opticalcoating 120 and any additional coatings, as described herein, exhibit ahardness of about 10 GPa or greater, or 11 GPa or greater, or about 12GPa or greater (e.g., 14 GPa or greater, 16 GPa or greater, 18 GPa orgreater, 20 GPa or greater), and about 50 GPa or less, for example about40 GPa or less, or about 30 GPa or less, as measured on the outersurface 22, by a Berkovich Indenter Hardness Test. The hardness of theoptical coating 120 may be up to about 20 GPa, 30 GPa, or 50 GPa. Suchmeasured hardness values may be exhibited by the optical coating 120and/or the article 100 along an indentation depth of about 50 nm orgreater or about 100 nm or greater (e.g., from about 100 nm to about 300nm, from about 100 nm to about 400 nm, from about 100 nm to about 500nm, from about 100 nm to about 600 nm, from about 200 nm to about 300nm, from about 200 nm to about 400 nm, from about 200 nm to about 500nm, or from about 200 nm to about 600 nm). In one or more embodiments,the article exhibits a hardness that is greater than the hardness of thesubstrate (which can be measured on the opposite surface from the outersurface).

The optical coating 120 may have at least one layer having a hardness(as measured on the surface of such layer, e.g., surface of thick highhardness portion 140, of about 12 GPa or greater, about 13 GPa orgreater, about 14 GPa or greater, about 15 GPa or greater, about 16 GPaor greater, about 17 GPa or greater, about 18 GPa or greater, about 19GPa or greater, about 20 GPa or greater, about 22 GPa or greater, about23 GPa or greater, about 24 GPa or greater, about 25 GPa or greater,about 26 GPa or greater, or about 27 GPa or greater (up to about 50GPa), as measured by the Berkovich Indenter Hardness Test. The hardnessof such layer may be in the range from about 18 GPa to about 21 GPa, asmeasured by the Berkovich Indenter Hardness Test. Such measured hardnessvalues may be exhibited by the at least one layer along an indentationdepth of about 50 nm or greater or 100 nm or greater (e.g., from about100 nm to about 300 nm, from about 100 nm to about 400 nm, from about100 nm to about 500 nm, from about 100 nm to about 600 nm, from about200 nm to about 300 nm, from about 200 nm to about 400 nm, from about200 nm to about 500 nm, or from about 200 nm to about 600 nm).

In one or more embodiments, the optical coating 120 or individual layerswithin the optical coating may exhibit an elastic modulus of about 75GPa or greater, about 80 GPa or greater or about 85 GPa or greater, asmeasured on the outer surface 122, by indenting that surface with aBerkovitch indenter. The optical coating 120 or individual layers withinthe optical coating may exhibit an elastic modulus of about 500 GPa orless. These modulus values may represent a modulus measured very closeto the outer surface, e.g. at indentation depths of 0 nm to about 50 nm,or it may represent a modulus measured at deeper indentation depths,e.g. from about 50 nm to about 1000 nm.

In some embodiments, the article comprises a maximum hardness in theranges described herein for the optical coating. For example, in someembodiments, the article comprises a maximum hardness in the range fromabout 12 GPa to about 30 Gpa, or about 16 Gpa to about 30 Gpa, whereinmaximum hardness is measured on the second major surface by indentingthe second major surface with a Berkovich indenter to form an indentcomprising an indentation depth of about 100 nm or more from the surfaceof the second major surface.

Chemical Nomenclature

As used herein, the “AlO_(x)N_(y),” “SiO_(x)N_(y),” and“Si_(u)Al_(x)O_(y)N_(z)” materials in the disclosure include variousaluminum oxynitride, silicon oxynitride and silicon aluminum oxynitridematerials, as understood by those with ordinary skill in the field ofthe disclosure, described according to certain numerical values andranges for the subscripts, “u,” “x,” “y,” and “z”. That is, it is commonto describe solids with “whole number formula” descriptions, such asAl₂O₃. It is also common to describe solids using an equivalent “atomicfraction formula” description such as Al_(0.4)O_(0.6), which isequivalent to Al₂O₃. In the atomic fraction formula, the sum of allatoms in the formula is 0.4+0.6=1, and the atomic fractions of Al and Oin the formula are 0.4 and 0.6 respectively. Atomic fractiondescriptions are described in many general textbooks and atomic fractiondescriptions are often used to describe alloys. See, for example: (i)Charles Kittel, Introduction to Solid State Physics, seventh edition,John Wiley & Sons, Inc., NY, 1996, pp. 611-627; (ii) Smart and Moore,Solid State Chemistry, An introduction, Chapman & Hall University andProfessional Division, London, 1992, pp. 136-151; and (iii) James F.Shackelford, Introduction to Materials Science for Engineers, SixthEdition, Pearson Prentice Hall, New Jersey, 2005, pp. 404-418.

Again referring to the “AlO_(x)N_(y),” “SiO_(x)N_(y),” and“Si_(u)Al_(x)O_(y)N_(z)” materials in the disclosure, the subscriptsallow those with ordinary skill in the art to reference these materialsas a class of materials without specifying particular subscript values.To speak generally about an alloy, such as aluminum oxide, withoutspecifying the particular subscript values, we can speak of Al_(v)O_(x).The description Al_(v)O_(x) can represent either Al₂O₃ orAl_(0.4)O_(0.6). If v+x were chosen to sum to 1 (i.e. v+x=1), then theformula would be an atomic fraction description. Similarly, morecomplicated mixtures can be described, such as Si_(u)Al_(v)O_(x)N_(y),where again, if the sum u+v+x+y were equal to 1, we would have theatomic fractions description case.

Once again referring to the “AlO_(x)N_(y),” “SiO_(x)N_(y),” and“Si_(u)Al_(x)O_(y)N_(z)” materials in the disclosure, these notationsallow those with ordinary skill in the art to readily make comparisonsto these materials and others. That is, atomic fraction formulas aresometimes easier to use in comparisons. For instance; an example alloyconsisting of (Al₂O₃)_(0.3)(AlN)_(0.7) is closely equivalent to theformula descriptions Al_(0.448)O_(0.31)N_(0.241) and also Al₃₆₇O₂₅₄N₁₉₈.Another example alloy consisting of (Al₂O₃)_(0.4)(AlN)_(0.6) is closelyequivalent to the formula descriptions Al_(0.438)O_(0.375)N_(0.188) andAl₃₇O₃₂N₁₆. The atomic fraction formulas Al_(0.448)O₀₃₁N_(0.241) andAl_(0.438)O_(0.375)N_(0.188) are relatively easy to compare to oneanother. For instance, Al decreased in atomic fraction by 0.01, Oincreased in atomic fraction by 0.065 and N decreased in atomic fractionby 0.053. It takes more detailed calculation and consideration tocompare the whole number formula descriptions Al₃₆₇O₂₅₄N₁₉₈ andAl₃₇O₃₂N₁₆. Therefore, it is sometimes preferable to use atomic fractionformula descriptions of solids. Nonetheless, the use of Al_(v)O_(x)N_(y)is general since it captures any alloy containing Al, 0 and N atoms.

As understood by those with ordinary skill in the field of thedisclosure with regard to any of the foregoing materials (e.g., AlN) forthe optical film 120, each of the subscripts, “u,” “x,” “y,” and “z,”can vary from 0 to 1, the sum of the subscripts will be less than orequal to one, and the balance of the composition is the first element inthe material (e.g., Si or Al). In addition, those with ordinary skill inthe field can recognize that “Si_(u)Al_(x)O_(y)N_(z)” can be configuredsuch that “u” equals zero and the material can be described as“AlO_(x)N_(y)”. Still further, the foregoing compositions for theoptical film 120 exclude a combination of subscripts that would resultin a pure elemental form (e.g., pure silicon, pure aluminum metal,oxygen gas, etc.). Finally, those with ordinary skill in the art willalso recognize that the foregoing compositions may include otherelements not expressly denoted (e.g., hydrogen), which can result innon-stoichiometric compositions (e.g., SiN_(x) vs. Si₃N₄). Accordingly,the foregoing materials for the optical film can be indicative of theavailable space within a SiO₂—Al₂O₃—SiN_(x)—AlN or aSiO₂—Al₂O₃—Si₃N₄—AlN phase diagram, depending on the values of thesubscripts in the foregoing composition representations.

Colors and Color Shift with Angle

In some cases the optical coating may be designed to have a relativelyneutral (grey or silver) color and a relatively small change in colorwith angle of light incidence.

Specifically, the hardcoated articles may exhibit a single-surfacereflected color range for all viewing angles from 0 to 60 degrees thatcomprises all a* and all b* points having absolute values of 20 or less,10 or less, 8 or less, 5 or less, 4 or less, 3 or less, or even 2 orless across all viewing angles.

Further, the hardcoated articles may have a two-surface transmittedcolor range for all viewing angles from 0 to 90 degrees that comprisesall a* and all b* points having absolute values of 2 or less, 1 or less,0.5 or less, 0.4 or less, 0.3 or less, or even 0.2 or less across allviewing angles.

The low reflectance and low color values described above are most suitedfor certain applications, for example protective covers for displays(smartwatches, smartphones, automotive displays, etc.) having highscratch resistance and low reflectance, which improves displayreadability in ambient lighting and can improve safety e.g. in anautomobile driving situation.

Optical interference between reflected waves from the optical coating120/air interface and the optical coating 120/substrate 110 interfacecan lead to spectral reflectance and/or transmittance oscillations thatcreate apparent color in the article 100. The color may be morepronounced in reflection. The angular color shifts in reflection withviewing angle due to a shift in the spectral reflectance oscillationswith incident illumination angle. Angular color shifts in transmittancewith viewing angle are also due to the same shift in the spectraltransmittance oscillation with incident illumination angle. The observedcolor and angular color shifts with incident illumination angle areoften distracting or objectionable to device users, particularly underillumination with sharp spectral features such as fluorescent lightingand some LED lighting. Angular color shifts in transmission may alsoplay a factor in color shift in reflection and vice versa. Factors inangular color shifts in transmission and/or reflection may also includeangular color shifts due to viewing angle or angular color shifts awayfrom a certain white point that may be caused by material absorption(somewhat independent of angle) defined by a particular illuminant ortest system.

As used herein, a “near normal” incidence angle means an incidence anglethat is 10 degrees or less from normal incidence. “Near normal” includesnormal. When a transmission or reflection criteria is described asoccurring at a “near normal” angle, the criteria is met if the specifiedtransmission or reflection criteria occurs at any near normal angle. Inmany cases, optical properties such as reflectance, transmission andcolor shift due to a multi-layer interference stack do not vary much asa function of angle at near normal angles. So, “near normal” incidenceand “normal” incidence are, for practical purposes, the same. Inaddition, some measurement techniques do not work well at exactly normalincident angles, so properties at normal incident angles are oftenestimated based on measurements at near normal angles. All occurrencesof “normal” incidence herein should be read as including “near normal.”

The oscillations may be described in terms of amplitude. As used herein,the term “amplitude” includes the peak-to-valley change in reflectanceor transmittance. The phrase “average amplitude” includes thepeak-to-valley change in reflectance or transmittance averaged overseveral oscillation cycles or wavelength sub-ranges within the opticalwavelength regime. As used herein, unless otherwise specified, the“optical wavelength regime” includes the wavelength range from about 400nm to about 700 nm (and more specifically from about 450 nm to about 650nm). In some embodiments, the article exhibits an average transmittanceor average reflectance comprising an average oscillation amplitude of 10percentage points or less, 8 percentage points or less, 6 percentagepoints or less, 4 percentage points or less, 2 percentage points orless, or 1 percentage point or less, over the optical wavelength regime.

One aspect of this disclosure pertains to an article that exhibits coloror colorlessness properties in reflectance and/or transmittance evenwhen viewed at different incident illumination angles under anilluminant. As used herein, the phrase “color shift” (angular orreference point) refers to the change in both a* and b*, under the CIEL*, a*, b* colorimetry system in reflectance and/or transmittance. Thiscolor shift is commonly referred to as C*, and is not affected by anychanges in L*. For example, angular color shift C* may be determinedusing the following Equation (1):

√((a* ₂ −a* ₁)²+(b* ₂ −b* ₁)²),

with a*₁, and b*₁ representing the a* and b* coordinates of the articlewhen viewed at incidence reference illumination angle (which may includenormal incidence) and a*₂, and b*₂ representing the a* and b*coordinates of the article when viewed at an incident illuminationangle, provided that the incident illumination angle is different fromthe reference illumination angle and in some cases differs from thereference illumination angle by about 1 degree or more, for example,about 2 degrees or about 5 degrees. In some instances, a specifiedangular color shift in reflectance and/or transmittance is exhibited bythe article when viewed at various incident illumination angles from areference illumination angle, under an illuminant. The illuminant caninclude standard illuminants as determined by the CIE, including Ailluminants (representing tungsten-filament lighting), B illuminants(daylight simulating illuminants), C illuminants (daylight simulatingilluminants), D series illuminants (representing natural daylight), andF series illuminants (representing various types of fluorescentlighting). Unless otherwise specified, color and color shift areexhibited under a D65 illuminant.

The reference illumination angle may include normal incidence (i.e.,from about 0 degrees to about 10 degrees), or 5 degrees from normalincidence, 10 degrees from normal incidence, 15 degrees from normalincidence, 20 degrees from normal incidence, 25 degrees from normalincidence, 30 degrees from normal incidence, 35 degrees from normalincidence, 40 degrees from normal incidence, 45 degrees from normalincidence, 50 degrees from normal incidence, 55 degrees from normalincidence, or 60 degrees from normal incidence, provided the differencebetween the incident illumination angle and the reference illuminationangle is about 1 degree or more, for example, about 2 degrees or about 5degrees. The incident illumination angle may be, with respect to thereference illumination angle, in the range from about 5 degrees to about80 degrees, from about 5 degrees to about 70 degrees, from about 5degrees to about 65 degrees, from about 5 degrees to about 60 degrees,from about 5 degrees to about 55 degrees, from about 5 degrees to about50 degrees, from about 5 degrees to about 45 degrees, from about 5degrees to about 40 degrees, from about 5 degrees to about 35 degrees,from about 5 degrees to about 30 degrees, from about 5 degrees to about25 degrees, from about 5 degrees to about 20 degrees, from about 5degrees to about 15 degrees, and all ranges and sub-ranges therebetween,away from the reference illumination angle. The article may exhibit theangular color shifts in reflectance and/or transmittance describedherein at and along all the incident illumination angles in the rangefrom about 0 degrees to about 60 degrees, or about 0 degrees to about 90degrees.

In some embodiments, the angular color shift may be measured at allangles between a reference illumination angle (e.g., normal incidence)and an incident illumination angle in the range from 0 degrees to about60 degrees, or about 0 degrees to about 90 degrees.

In one or more embodiments, the reference point for measuring colorshift may be the origin (0, 0) in the CIE L*, a*, b* colorimetry system(or the color coordinates a*=0, b*=0), or the transmittance orreflectance color coordinates of the substrate. Unless otherwisespecified, the reference point is the color coordinates a*=0, b*=0. Itshould be understood that unless otherwise noted, the L* coordinate ofthe articles described herein does not affect color shift calculated asdescribed herein. Where the reference point color shift of the articleis defined with respect to the substrate, the transmittance colorcoordinates of the article are compared to the transmittance colorcoordinates of the substrate and the reflectance color coordinates ofthe article are compared to the reflectance color coordinates of thesubstrate.

Where the reference point is the color coordinates a*=0, b*=0, thereference point color shift is calculated by Equation (2).

reference point color shift=√g((a* _(article))²+(b* _(article))²)

Where the reference point is the color coordinates of the substrate, thereference point color shift is calculated by Equation (4).

reference point color shift=√((a* _(article) −a* _(substrate))²+(b*_(article) −b* _(substrate))²)

In some embodiments, the article may exhibit a transmittance color (ortransmittance color coordinates) and a reflectance color (or reflectancecolor coordinates) such that the reference point color shift is asspecified when the reference point is any one of the color coordinatesof the substrate, and the color coordinates a*=0, b*=0.

In some embodiments, the article exhibits a specified a* value intransmittance (at the outer surface and the opposite bare surface) atincident illumination angles in the range from about 0 degrees to about60 degrees under illuminants D65, A, and F2. In some embodiments, thearticle exhibits a specified b* value in transmittance (at the outersurface and the opposite bare surface) at incident illumination anglesin the range from about 0 degrees to about 60 degrees under illuminantsD65, A, and F2.

In some embodiments, the article exhibits a specified a* value inreflectance (at only the outer surface) at incident illumination anglesin the range from about 0 degrees to about 60 degrees under illuminantsD65, A, and F2. In some embodiments, the article exhibits a specified b*value in reflectance (at only the outer surface) at incidentillumination angles in the range from about 0 degrees to about 60degrees under illuminants D65, A, and F2.

A maximum reflectance color shift values represent the lowest colorpoint value measured in a specified range of angles, subtracted from thehighest color point value measured at any angle in the same range. Thevalues may represent a maximum change in a* value(a*_(highest)−a*_(lowest)), a maximum change in b* value(b*_(highest)−b*_(lowest)), a maximum change in both a* and b* values,or a maximum change in the quantity√((a*_(highest)−a*_(lowest))²+(b*_(highest)−b*_(lowest))²). Unlessotherwise specified, maximum reflectance color shift refers to a maximumchange in this quantity.

Photopic Average Reflectance and Transmittance

In some embodiments, the article of one or more embodiments, or theouter surface 122 of one or more articles, may exhibit a specifiedaverage visible photopic average reflectance and/or average visiblephotopic average transmittance over the optical wavelength regime. Thesephotopic reflectance values may be exhibited at incident illuminationangles in the range from about 0° to about 20°, from about 0° to about40° or from about 0° to about 60°. Unless otherwise specified, theaverage photopic average reflectance or transmittance is measured at anincident illumination angle in the range from about 0 degrees to about10 degrees. As used herein, photopic average reflectance mimics theresponse of the human eye by weighting the reflectance versus wavelengthspectrum according to the human eye's sensitivity. Photopic averagereflectance is defined as the luminance, or tristimulus Y value ofreflected light, according to CIE color space conventions. The averagephotopic average reflectance is defined in Equation (4) as the spectralreflectance, R(λ) multiplied by the illuminant spectrum, I(λ) and theCIE's color matching function y(λ), related to the eye's spectralresponse:

$\left\langle R_{p} \right\rangle = {\int\limits_{380{nm}}^{720{nm}}{{R(\lambda)} \times {I(\lambda)} \times {\overset{\_}{y}(\lambda)}d\lambda}}$

In some embodiments, the article exhibits a specified single-sideaverage photopic reflectance, measured at normal or near-normalincidence (e.g. 0-10 degrees) on the outer surface only.

Substrate

The substrate 110 may include an inorganic material and may include anamorphous substrate, a crystalline substrate or a combination thereof.The substrate 110 may be formed from man-made materials and/or naturallyoccurring materials (e.g., quartz and polymers). For example, in someinstances, the substrate 110 may be characterized as organic and mayspecifically be polymeric. Examples of suitable polymers include,without limitation: thermoplastics including polystyrene (PS) (includingstyrene copolymers and blends), polycarbonate (PC) (including copolymersand blends), polyesters (including copolymers and blends, includingpolyethyleneterephthalate and poly ethyleneterephthalate copolymers),polyolefins (PO) and cyclicpolyolefins (cyclic-PO), polyvinylchloride(PVC), acrylic polymers including polymethyl methacrylate (PMMA)(including copolymers and blends), thermoplastic urethanes (TPU),polyetherimide (PEI) and blends of these polymers with each other. Otherexemplary polymers include epoxy, styrenic, phenolic, melamine, andsilicone resins.

In some specific embodiments, the substrate 110 may specifically excludepolymeric, plastic and/or metal substrates. The substrate may becharacterized as alkali-including substrates (i.e., the substrateincludes one or more alkalis). In one or more embodiments, the substrateexhibits a refractive index in the range from about 1.45 to about 1.55.In specific embodiments, the substrate 110 may exhibit an averagestrain-to-failure at a surface on one or more opposing major surfacethat is 0.5% or greater, 0.6% or greater, 0.7% or greater, 0.8% orgreater, 0.9% or greater, 1% or greater, 1.1% or greater, 1.2% orgreater, 1.3% or greater, 1.4% or greater 1.5% or greater or even 2% orgreater, as measured using ball-on-ring testing using 5 or more,samples. More samples may be used, within reason, as it is expected thata greater number of samples will lead to greater statisticalconsistency. In specific embodiments, the substrate 110 may exhibit anaverage strain-to-failure at its surface on one or more opposing majorsurface of about 1.2%, about 1.4%, about 1.6%, about 1.8%, about 2.2%,about 2.4%, about 2.6%, about 2.8%, or about 3% or greater.

Suitable substrates 110 may exhibit an elastic modulus (or Young'smodulus) in the range from about 30 GPa to about 120 GPa. In someinstances, the elastic modulus of the substrate may be in the range fromabout 30 GPa to about 110 GPa, from about 30 GPa to about 100 GPa, fromabout 30 GPa to about 90 GPa, from about 30 GPa to about 80 GPa, fromabout 30 GPa to about 70 GPa, from about 40 GPa to about 120 GPa, fromabout 50 GPa to about 120 GPa, from about 60 GPa to about 120 GPa, fromabout 70 GPa to about 120 GPa, and all ranges and sub-rangestherebetween.

In one or more embodiments, the amorphous substrate may include glass,which may be strengthened or non-strengthened. Examples of suitableglass include soda lime glass, alkali aluminosilicate glass, alkalicontaining borosilicate glass and alkali aluminoborosilicate glass. Insome variants, the glass may be free of lithia. In one or morealternative embodiments, the substrate 110 may include crystallinesubstrates such as glass ceramic substrates (which may be strengthenedor non-strengthened) or may include a single crystal structure, such assapphire. In one or more specific embodiments, the substrate 110includes an amorphous base (e.g., glass) and a crystalline cladding(e.g., sapphire layer, a polycrystalline alumina layer and/or or aspinel (MgAl₂O₄) layer).

The substrate 110 of one or more embodiments may have a hardness that isless than the hardness of the article (as measured by the BerkovichIndenter Hardness Test described herein). The hardness of the substrateis determined by the Berkovich Indenter Hardness Test, as describedherein.

The substrate 110 may be substantially planar or sheet-like, althoughother embodiments may utilize a curved or otherwise shaped or sculptedsubstrate. The substrate 110 may be substantially optically clear,transparent and free from light scattering. In such embodiments, thesubstrate may exhibit an average light transmission over the opticalwavelength regime of about 85% or greater, about 86% or greater, about87% or greater, about 88% or greater, about 89% or greater, about 90% orgreater, about 91% or greater or about 92% or greater. In one or morealternative embodiments, the substrate 110 may be opaque or exhibit anaverage light transmission over the optical wavelength regime of lessthan about 10%, less than about 9%, less than about 8%, less than about7%, less than about 6%, less than about 5%, less than about 4%, lessthan about 3%, less than about 2%, less than about 1%, or less thanabout 0.5%. In some embodiments, these light reflectance andtransmittance values may be a total reflectance or total transmittance(taking into account reflectance or transmittance on both major surfacesof the substrate) or may be observed on a single side of the substrate(i.e., on the outer surface 122 only, without taking into account theopposite surface). Unless otherwise specified, the average reflectanceor transmittance is measured at an incident illumination angle of 0degrees (however, such measurements may be provided at incidentillumination angles of 45 degrees or 60 degrees). The substrate 110 mayoptionally exhibit a color, such as white, black, red, blue, green,yellow, orange etc.

Additionally or alternatively, the physical thickness of the substrate110 may vary along one or more of its dimensions for aesthetic and/orfunctional reasons. For example, the edges of the substrate 110 may bethicker as compared to more central regions of the substrate 110. Thelength, width and physical thickness dimensions of the substrate 110 mayalso vary according to the application or use of the article 100.

The substrate 110 may be provided using a variety of differentprocesses. For instance, where the substrate 110 includes an amorphoussubstrate such as glass, various forming methods can include float glassprocesses and down-draw processes such as fusion draw and slot draw.

Once formed, a substrate 110 may be strengthened to form a strengthenedsubstrate. As used herein, the term “strengthened substrate” may referto a substrate that has been chemically strengthened, for examplethrough ion-exchange of larger ions for smaller ions in the surface ofthe substrate. However, other strengthening methods known in the art,such as thermal tempering, or utilizing a mismatch of the coefficient ofthermal expansion between portions of the substrate to createcompressive stress and central tension regions, may be utilized to formstrengthened substrates.

Where the substrate is chemically strengthened by an ion exchangeprocess, the ions in the surface layer of the substrate are replacedby—or exchanged with—larger ions having the same valence or oxidationstate. Ion exchange processes are typically carried out by immersing asubstrate in a molten salt bath containing the larger ions to beexchanged with the smaller ions in the substrate. It will be appreciatedby those skilled in the art that parameters for the ion exchangeprocess, including, but not limited to, bath composition andtemperature, immersion time, the number of immersions of the substratein a salt bath (or baths), use of multiple salt baths, additional stepssuch as annealing, washing, and the like, are generally determined bythe composition of the substrate and the desired compressive stress(CS), depth of compressive stress layer (or depth of layer) of thesubstrate that result from the strengthening operation. By way ofexample, ion exchange of alkali metal-containing glass substrates may beachieved by immersion in at least one molten bath containing a salt suchas, but not limited to, nitrates, sulfates, and chlorides of the largeralkali metal ion. The temperature of the molten salt bath typically isin a range from about 380° C. up to about 450° C., while immersion timesrange from about 15 minutes up to about 40 hours. However, temperaturesand immersion times different from those described above may also beused.

In addition, non-limiting examples of ion exchange processes in whichglass substrates are immersed in multiple ion exchange baths, withwashing and/or annealing steps between immersions, are described in U.S.patent application Ser. No. 12/500,650, filed Jul. 10, 2009, by DouglasC. Allan et al., entitled “Glass with Compressive Surface for ConsumerApplications” and claiming priority from U.S. Provisional PatentApplication No. 61/079,995, filed Jul. 11, 2008, in which glasssubstrates are strengthened by immersion in multiple, successive, ionexchange treatments in salt baths of different concentrations; and U.S.Pat. No. 8,312,739, by Christopher M. Lee et al., issued on Nov. 20,2012, and entitled “Dual Stage Ion Exchange for Chemical Strengtheningof Glass,” and claiming priority from U.S. Provisional PatentApplication No. 61/084,398, filed Jul. 29, 2008, in which glasssubstrates are strengthened by ion exchange in a first bath is dilutedwith an effluent ion, followed by immersion in a second bath having asmaller concentration of the effluent ion than the first bath. Thecontents of U.S. patent application Ser. No. 12/500,650 and U.S. Pat.No. 8,312,739 are incorporated herein by reference in their entirety.

Compressive stress (including surface CS) is measured by surface stressmeter (FSM) using commercially available instruments such as theFSM-6000, manufactured by Orihara Industrial Co., Ltd. (Japan). Surfacestress measurements rely upon the accurate measurement of the stressoptical coefficient (SOC), which is related to the birefringence of theglass. SOC in turn is measured according to Procedure C (Glass DiscMethod) described in ASTM standard C770-16, entitled “Standard TestMethod for Measurement of Glass Stress-Optical Coefficient,” thecontents of which are incorporated herein by reference in theirentirety. Maximum CT values are measured using a scattered lightpolariscope (SCALP) technique known in the art.

As used herein, DOC means the depth at which the stress in thechemically strengthened alkali aluminosilicate glass article describedherein changes from compressive to tensile. DOC may be measured by FSMor a scattered light polariscope (SCALP) depending on the ion exchangetreatment. Where the stress in the glass article is generated byexchanging potassium ions into the glass article, FSM is used to measureDOC. Where the stress is generated by exchanging sodium ions into theglass article, SCALP is used to measure DOC. Where the stress in theglass article is generated by exchanging both potassium and sodium ionsinto the glass, the DOC is measured by SCALP, since it is believed theexchange depth of sodium indicates the DOC and the exchange depth ofpotassium ions indicates a change in the magnitude of the compressivestress (but not the change in stress from compressive to tensile); theexchange depth of potassium ions in such glass articles is measured byFSM.

In some embodiments, a strengthened substrate 110 can have a surface CSof 250 MPa or greater, 300 MPa or greater, e.g., 400 MPa or greater, 450MPa or greater, 500 MPa or greater, 550 MPa or greater, 600 MPa orgreater, 650 MPa or greater, 700 MPa or greater, 750 MPa or greater or800 MPa or greater. The strengthened substrate may have a DOC of 10 μmor greater, 15 μm or greater, 20 μm or greater (e.g., 25 μm, 30 μm, 35μm, 40 μm, 45 μm, 50 μm or greater) and/or a maximum CT of 10 MPa orgreater, 20 MPa or greater, 30 MPa or greater, 40 MPa or greater (e.g.,42 MPa, 45 MPa, or 50 MPa or greater) but less than 100 MPa (e.g., 95,90, 85, 80, 75, 70, 65, 60, 55 MPa or less). In one or more specificembodiments, the strengthened substrate has one or more of thefollowing: a surface CS greater than 500 MPa, a DOC greater than 15 μm,and a maximum CT greater than 18 MPa.

Example glasses that may be used in the substrate may include alkalialuminosilicate glass compositions or alkali aluminoborosilicate glasscompositions, though other glass compositions are contemplated. Suchglass compositions are capable of being chemically strengthened by anion exchange process. One example glass composition comprises SiO₂, B₂O₃and Na₂O, where (SiO₂+B₂O₃)≥66 mol. %, and Na₂O≥9 mol. %. In someembodiments, the glass composition includes 6 wt. % or more aluminumoxide. In further embodiments, the substrate includes a glasscomposition with one or more alkaline earth oxides, such that a contentof alkaline earth oxides is 5 wt. % or more. Suitable glasscompositions, in some embodiments, further comprise at least one of K₂O,MgO, and CaO. In some embodiments, the glass compositions used in thesubstrate can comprise 61-75 mol. % SiO2; 7-15 mol. % Al₂O₃; 0-12 mol. %B₂O₃; 9-21 mol. % Na₂O; 0-4 mol. % K₂O; 0-7 mol. % MgO; and 0-3 mol. %CaO.

A further example glass composition suitable for the substratecomprises: 60-70 mol. % SiO₂; 6-14 mol. % Al₂O₃; 0-15 mol. % B₂O₃; 0-15mol. % Li₂O; 0-20 mol. % Na₂O; 0-10 mol. % K₂O; 0-8 mol. % MgO; 0-10mol. % CaO; 0-5 mol. % ZrO₂; 0-1 mol. % SnO₂; 0-1 mol. % CeO₂; less than50 ppm As₂O₃; and less than 50 ppm Sb₂O₃; where 12 mol.%≤(Li₂O+Na₂O+K₂O)≤20 mol. % and 0 mol. %≤(MgO+CaO)≤10 mol. %.

A still further example glass composition suitable for the substratecomprises: 63.5-66.5 mol. % SiO₂; 8-12 mol. % Al₂O₃; 0-3 mol. % B₂O₃;0-5 mol. % Li₂O; 8-18 mol. % Na₂O; 0-5 mol. % K₂O; 1-7 mol. % MgO; 0-2.5mol. % CaO; 0-3 mol. % ZrO₂; 0.05-0.25 mol. % SnO₂; 0.05-0.5 mol. %CeO₂; less than 50 ppm As₂O₃; and less than 50 ppm Sb₂O₃; where 14 mol.%≤(Li₂O+Na₂O+K₂O)≤18 mol. % and 2 mol. %≤(MgO+CaO)≤7 mol. %.

In some embodiments, an alkali aluminosilicate glass compositionsuitable for the substrate comprises alumina, at least one alkali metaland, in some embodiments, greater than 50 mol. % SiO₂, in otherembodiments 58 mol. % or more SiO₂, and in still other embodiments 60mol. % or more SiO₂, wherein the ratio (Al₂O₃+B₂O₃)/Σmodifiers (i.e.,sum of modifiers) is greater than 1, where in the ratio the componentsare expressed in mol. % and the modifiers are alkali metal oxides. Thisglass composition, in particular embodiments, comprises: 58-72 mol. %SiO₂; 9-17 mol. % Al₂O₃; 2-12 mol. % B₂O₃; 8-16 mol. % Na₂O; and 0-4mol. % K₂O, wherein the ratio (Al₂O₃+B₂O₃)/Σmodifiers (i.e., sum ofmodifiers) is greater than 1.

In some embodiments, the substrate may include an alkali aluminosilicateglass composition comprising: 64-68 mol. % SiO₂; 12-16 mol. % Na₂O; 8-12mol. % Al₂O₃; 0-3 mol. % B₂O₃; 2-5 mol. % K₂O; 4-6 mol. % MgO; and 0-5mol. % CaO, wherein: 66 mol. %≤SiO₂+B₂O₃+CaO≤69 mol. %;Na₂O+K₂O+B₂O₃+MgO+CaO+SrO>10 mol. %; 5 mol. %≤MgO+CaO+SrO≤8 mol. %;(Na₂O+B₂O₃)—Al₂O₃≤2 mol. %; 2 mol. %≤Na₂O— Al₂O₃≤6 mol. %; and 4 mol.%≤(Na₂O+K₂O)— Al₂O₃≤10 mol. %.

In some embodiments, the substrate may comprise an alkalialuminosilicate glass composition comprising: 2 mol % or more of Al₂O₃and/or ZrO₂, or 4 mol % or more of Al₂O₃ and/or ZrO₂.

Where the substrate 110 includes a crystalline substrate, the substratemay include a single crystal, which may include Al₂O₃. Such singlecrystal substrates are referred to as sapphire. Other suitable materialsfor a crystalline substrate include polycrystalline alumina layer and/orspinel (MgAl₂O₄).

Optionally, the crystalline substrate 110 may include a glass ceramicsubstrate, which may be strengthened or non-strengthened. Examples ofsuitable glass ceramics may include Li₂O—Al₂O₃—SiO₂ system (i.e.LAS-System) glass ceramics, MgO—Al₂O₃—SiO₂ system (i.e. MAS-System)glass ceramics, and/or glass ceramics that include a predominant crystalphase including β-quartz solid solution, β-spodumene ss, cordierite, andlithium disilicate. The glass ceramic substrates may be strengthenedusing the chemical strengthening processes disclosed herein. In one ormore embodiments, MAS-System glass ceramic substrates may bestrengthened in Li₂SO₄ molten salt, whereby an exchange of 2Li⁺ for Mg²⁺can occur.

The substrate 110 according to one or more embodiments can have aphysical thickness ranging from about 100 μm to about 5 mm. Examplesubstrate 110 physical thicknesses range from about 100 μm to about 500μm (e.g., 100, 200, 300, 400 or 500 μm). Further example substrate 110physical thicknesses range from about 500 μm to about 1000 μm (e.g.,500, 600, 700, 800, 900 or 1000 μm). The substrate 110 may have aphysical thickness greater than about 1 mm (e.g., about 2, 3, 4, or 5mm). In one or more specific embodiments, the substrate 110 may have aphysical thickness of 2 mm or less or less than 1 mm. The substrate 110may be acid polished or otherwise treated to remove or reduce the effectof surface flaws.

Methods

A second aspect of this disclosure pertains to a method for forming thearticles described herein. In some embodiments, the method includesproviding a substrate having a major surface in a coating chamber,forming a vacuum in the coating chamber, forming a durable opticalcoating as described herein on the major surface, optionally forming anadditional coating comprising at least one of an easy-to-clean coatingand a scratch resistant coating, on the optical coating, and removingthe substrate from the coating chamber. In one or more embodiments, theoptical coating and the additional coating are formed in either the samecoating chamber or without breaking vacuum in separate coating chambers.

In one or more embodiments, the method may include loading the substrateon carriers which are then used to move the substrate in and out ofdifferent coating chambers, under load lock conditions so that a vacuumis preserved as the substrate is moved.

The optical coating 120 and/or other layers may be formed using variousdeposition methods such as vacuum deposition techniques, for example,chemical vapor deposition (e.g., plasma enhanced chemical vapordeposition (PECVD), low-pressure chemical vapor deposition, atmosphericpressure chemical vapor deposition, and plasma-enhanced atmosphericpressure chemical vapor deposition), physical vapor deposition (e.g.,reactive or nonreactive sputtering, metal-mode reactive sputtering, orlaser ablation), thermal or e-beam evaporation and/or atomic layerdeposition. Liquid-based methods may also be used such as spraying,dipping, spin coating, or slot coating (for example, using sol-gelmaterials). Where vacuum deposition is utilized, inline processes may beused to form the optical coating 120 and/or other layers in onedeposition run. In some instances, the vacuum deposition can be made bya linear PECVD source.

In some embodiments, the method may include controlling the thickness ofthe optical coating 120 and/or other layers so that it does not vary bymore than about 4% along about 80% or more of the area of surface 122 orfrom the target thickness for each layer at any point along thesubstrate area. In some embodiments, the thickness of the opticalcoating 120 and/or other layers does not vary by more than about 4%along about 95% or more of the area of the outer surface 122.

In some embodiments, for any of the embodiments described herein, amethod of forming an article comprises: obtaining a substrate comprisinga first major surface and comprising an amorphous substrate or acrystalline substrate; disposing an optical coating on the first majorsurface, the optical coating comprising a second major surface oppositethe first major surface and a thickness in a direction normal to thesecond major surface; and creating a refractive index gradient along atleast a first gradient portion of the thickness of the optical coating.A refractive index of the optical coating varies along a thickness ofthe optical coating between the first major surface and the second majorsurface.

In some embodiments, for any of the embodiments described herein,creating a refractive index gradient comprises varying along thethickness of the optical coating at least one of the composition and theporosity of the optical coating. The composition and/or porosity may bevaried stepwise or continuously by adjusting deposition parameters andconditions in a stepwise or continuous manner.

Examples of Specific Articles

FIG. 45 shows glasses 4500 in accordance with some embodiments. Glasses4500 include lenses 4510, frames 4520, a bridge 4530, and temples 4540.Any suitable glasses structure may be used. The specific structure ofFIG. 45 is not intended to be limiting. For example, some glasses have asingle continuous lens as opposed to two lenses separate by a bridge.And, for example, some sunglasses have different frame configurations,including half-frame and no-frame configurations. In some embodiments, ascratch resistant coating as described herein may be applied to thefront surface of lenses 4510, i.e., the surface facing away from thewearer. Coatings may also be applied to the back surface of lenses 4510as described herein.

The glass articles disclosed herein may be incorporated into anotherarticle such as an article with a display (or display articles) (e.g.,consumer electronics, including mobile phones, tablets, computers,navigation systems, wearable devices (e.g., watches) and the like),architectural articles, transportation articles (e.g., automotive,trains, aircraft, sea craft, etc.), appliance articles, or any articlethat may benefit from some transparency, scratch-resistance, abrasionresistance or a combination thereof. The transparency may includevisible/optical transparency, or may include microwave/RF transparency(even if the article is opaque in the visible spectrum, such as for ablack glass-ceramic). An exemplary article incorporating any of theglass articles disclosed herein is shown in FIGS. 46 and 47 .Specifically, FIGS. 46 and 47 show a consumer electronic device 4600including a housing 4602 having front 4604, back 4606, and side surfaces4608; electrical components (not shown) that are at least partiallyinside or entirely within the housing and including at least acontroller, a memory, and a display 4610 at or adjacent to the frontsurface of the housing; and a cover substrate 4612 at or over the frontsurface of the housing such that it is over the display. In someembodiments, the cover substrate 4612 may include any of the glassarticles disclosed herein. In some embodiments, at least one of aportion of the housing or the cover substrate comprises the glassarticles disclosed herein.

EXAMPLES

Various embodiments will be further clarified by the following examples.

It has been observed through a variety of scratching, indentation, anddelamination experiments that gradient interfaces can provide improvedresistance to mechanical damage, including delamination. It is expectedthat a gradient with a lower slope (slowest compositional change) willact the most like a bulk material and thus have the highest resistanceto delamination. But, as explained further herein and illustrated by theexamples and comparative examples, gradients with very low slope may notbe able to achieve desired optical interference effects to generatedesired reflectance and other optical properties with dense coatingmaterials. The examples herein show that RI gradients with anappropriate slope can enhanced mechanical robustness, while still havingrefractive index changes that are rapid enough to provide desiredoptical interference effects. The most desirable embodiments will dependon application requirements. Some applications might require the highestmechanical performance while tolerating a higher reflectance; otherapplications may require a lower reflectance while tolerating a highercolor; and so on.

Comparative Examples 1-2 and Modeled Examples 1-5 used modeling todemonstrate the reflectance and transmittance spectra of articles thatincluded embodiments of the optical coating, as described herein. InComparative Examples 1-2 and Modeled Examples 1-5, unless otherwisespecified, the optical coating included layers of AlOxNy, SiO₂, andmixtures thereof. The substrate modeling parameters were based on aglass substrate commercially available from Corning® (Corning glass code5318).

The refractive index dispersion curves for the coating materials used inthe modeling were based on measured values. Single films of SiO₂ andAlO_(x)N_(y) were formed by metal-mode rotary drum reactive sputteringon fusion-formed and ion-exchanged 5318 glass. The AlO_(x)N_(y)fabricated and used in the modeled examples had a nominal composition ofabout 10-16 atomic % oxygen (˜12 wt % oxygen), 32-40 atomic % nitrogen,and 48-54 atomic % aluminum. Refractive indices for these single filmswere measured using spectroscopic ellipsometry. The results of thesemeasurements are shown in Table 2. Linear averages of the SiO₂ andAlO_(x)N_(y) refractive indices were used for the intermediate indexmixed materials in some of the Examples. In summary, these refractiveindices were measured from experimentally fabricated materials, with themodeled examples using optically simulated coating designs based on theexperimental refractive indices listed here. The modeled examples use asingle refractive index value in their descriptive tables forconvenience, which corresponds to a point selected from the dispersioncurves at about 550 nm wavelength.

TABLE 2 Measured Refractive Indices of 5318 Glass Substrate, SiO₂sputtered film, and AlO_(x)N_(y) sputtered film 5318 Glass substrateSiO2 sputtered film AlOxNy sputtered film Wavelength WavelengthWavelength (nm) n k (nm) n k (nm) n k 380.8 1.5244 0 375 1.498631.00E−05 375 2.0719 1.10E−04 400.9 1.5214 0 400 1.4949 1.00E−05 4002.0554 3.00E−05 421.0 1.5191 0 425 1.49176 1.00E−05 425 2.0425 1.00E−05451.2 1.5160 0 450 1.4890 0 450 2.0322 0 471.2 1.5143 0 475 1.48663 0475 2.0238 0 501.3 1.5126 0 500 1.4846 0 500 2.0169 0 521.4 1.5112 0 5251.48274 0 525 2.011 0 551.5 1.5100 0 550 1.4811 0 550 2.0061 0 571.51.5092 0 575 1.47973 0 575 2.0018 0 601.6 1.5083 0 600 1.4785 0 6001.9981 0 621.7 1.5075 0 625 1.47735 0 625 1.9949 0 651.7 1.5063 0 6501.4764 0 650 1.9921 0 671.8 1.5056 0 675 1.47546 0 675 1.9897 0 701.81.5045 0 700 1.4747 0 700 1.9875 0 719.8 1.5046 0 725 1.47392 0 7251.9855 0

In the examples, thicknesses are physical thickness, not opticalthicknesses. The structures of Examples 1 through 5 look similar to thatof FIG. 5 , but with the specific layers, layer compositions, and layerthicknesses provided in the examples.

In the examples, the outer surface may also be referred to as the“front” surface, and is the surface opposite the substrate. Single-sidedreflectance and single-sided reflected color are measured on the front(coated) surface while removing the reflectance from the backside of thecoated article, typically accomplished by optical coupling of the backsurface to an absorbing substrate. Transmittance is measured for lightpassing through the front surface toward the substrate. For example, ifthe examples were used on the outward facing surface of eyeglasses,transmission through the outer or front surface would be what the wearersees, and reflection from the outer or front surface would be whatothers see. The modeled examples were simulated using a CIE D65illuminant and D65 detector.

Reflectance and transmittance plots for the modeled examples werecalculated at 0 degrees (normal incidence), unless otherwise noted. Inpractice there is negligible change in optical performance from 0 to 10degrees, meaning normal incidence and near-normal incidence can beconsidered functionally equivalent, as defined by this 0-10 degreeangular range. Average polarization was used for all reflectance,transmittance, and color calculations.

In all of the examples of this disclosure, the thickness of the thickesthard layer (2000 nm in Example 1, 1200 nm in Example 3) can be varied toany value from 500 nm to 5000 nm without significantly changing theoptical performance. Similarly, the thickest hard layer can be comprisedof multiple sub-layers, for example <10 nm layers forming a‘superlattice’, while maintaining a high hardness and similar effectiveoptical performance.

In plots showing the structure of examples and comparative examples, theglass substrate is to the left. The thickness axis is centered with 0marking the beginning of the thickest hard layer. The gradient portionsof the coating are modeled as a series of discrete small steps inthickness and index. It should be recognized that continuous gradientswith similar gradient slopes, or a gradient having different discretestep sizes but a similar overall slope, can be designed to havesubstantially the same optical performance.

Comparative Example 1

Table 3 shows the structure of Comparative Example 1. ComparativeExample 1 has a discrete layered structure.

TABLE 3 Comparative Example 1, Structure Thickness Refractive IndexLayer (nm) @550 nm 5318 Glass Substrate 1.51 AlOxNy 8 2.006 SiO2 52.41.481 AlOxNy 24.5 2.006 SiO2 30.1 1.481 AlOxNy 42.6 2.006 SiO2 8.9 1.481AlOxNy 2000 2.006 SiO2 15 1.481 AlOxNy 30 2.006 SiO2 99 1.481 Air Medium1

Table 4 shows 1-side reflected color, 2-side transmitted color, photopicaverage reflectance, and photopic average transmittance for ComparativeExample 1.

TABLE 4 Comp. Ex. 1 1st-surface Reflectance Photopic Incident AverageReflected Reflected Angle (deg) % R (D65) a* (D65) b* (D65) 0 1.475−1.683 −2.108 6 1.470 −1.675 −2.098 10 1.463 −1.659 −2.080 20 1.444−1.522 −2.005 30 1.489 −1.137 −1.845 40 1.777 −0.456 −1.421 50 2.7630.272 −0.747 60 5.637 0.666 −0.120 70 13.653 0.665 0.189 80 35.987 0.3910.173 90 100 0 0 Comp. Ex. 1 2nd-surface Transmittance Photopic IncidentAverage Transmitted Transmitted Angle (deg) % T (D65) a* (D65) b* (D65)0 94.57 0.092 0.209 6 94.57 0.092 0.208 10 94.58 0.090 0.207 20 94.580.082 0.201 30 94.43 0.061 0.194 40 93.82 0.024 0.177 50 91.96 −0.0280.145 60 86.95 −0.083 0.098 70 74.41 −0.117 0.056 80 46.48 −0.105 0.05090 0 0 0

FIG. 7 shows the coating design of Comparative Example 1 as a plot ofRefractive Index vs. position. FIG. 8 shows detail for a part of thecoating design of Comparative Example 1 as a plot of Refractive Indexvs. position. FIG. 9 shows reflectance spectra for ComparativeExample 1. FIG. 10 shows transmittance spectra for ComparativeExample 1. FIG. 11 shows a plot of surface reflected D65 color vs. anglefor Comparative Example 1. FIG. 9 and FIG. 11 are based on incidentlight passing right to left in FIG. 7 .

Comparative Example 2

Table 5 shows the structure of Comparative Example 2. ComparativeExample 2 has a simple gradient which resulted in a relatively highreflectance.

TABLE 5 Comparative Example 2, Structure Thickness Refractive IndexLayer (nm) @550 nm 5318 Glass Substrate 1.51 Linear Gradient 640 Gradedfrom w/RI slope 1.51 to 2.006 in of = +0.0008/nm steps of 20 nm AlOxNy2000  2.006 Linear Gradient 125 Graded from w/RI slope 2.006 to 1.481 inof = −0.0043/nm steps of 3.66 nm Air Medium 1

Table 6 shows 1-side reflected color, 2-side transmitted color, photopicaverage reflectance, and photopic average transmittance for ComparativeExample 2.

TABLE 6 Comp. Ex. 2, 1st-surface Reflectance Photopic Incident AverageReflected Reflected Angle (deg) % R (D65) a* (D65) b* (D65) 0 3.34 1.45−3.51 6 3.34 1.48 −3.47 10 3.34 1.51 −3.39 20 3.38 1.67 −3.02 30 3.541.86 −2.33 40 4.04 1.97 −1.37 50 5.39 1.84 −0.27 60 8.84 1.47 0.56 7017.50 0.92 0.80 80 39.64 0.38 0.55 90 100 0 0 Comp. Ex. 2, 2-surfaceTransmittance Photopic Incident Average Transmitted Transmitted Angle(deg) % T (D65) a* (D65) b* (D65) 0 92.85 −0.15 0.46 6 92.85 −0.15 0.4510 92.85 −0.16 0.44 20 92.79 −0.18 0.41 30 92.56 −0.20 0.34 40 91.83−0.23 0.24 50 89.83 −0.24 0.12 60 84.75 −0.24 −0.02 70 72.43 −0.19 −0.1280 45.26 −0.11 −0.16 90 0.00 0.00 0.00

FIG. 12 shows the coating design of Comparative Example 2 as a plot ofRefractive Index vs. position. FIG. 13 shows detail for a part of thecoating design of Comparative Example 2 as a plot of Refractive Indexvs. position. FIG. 14 shows reflectance spectra for Comparative Example2. FIG. 15 shows transmittance spectra for Comparative Example 2. FIG.16 shows a plot of surface reflected D65 color vs. angle for ComparativeExample 2. FIG. 14 and FIG. 16 are based on incident light passing rightto left in FIG. 12 .

Example 1

Example 1 comprises a hardcoated, chemically strengthened glass havingan anti-reflective top portion to the hardcoating. This anti-reflectivetop portion comprises a gradient layer that is 33 nm thick comprising agradual change in refractive index from 2.006 to 1.481 as furtherdetailed in above tables and figures, followed by a top-most ‘cap’ layerof 78 nm thickness having an index of 1.481 (e.g. sputtered SiO₂). This33 nm gradient layer and 78 nm cap layer function together to provide anoptical-interference-based anti-reflective effect, while also removingabrupt interfaces for mechanical performance improvement. Example 1 has1-surface reflectance of 0.31% at 550 nm wavelength, 1-surfacereflectance below 0.5% for the entire range from 525 to 590 nmwavelength, 1-surface average reflectance of 0.42% over the wavelengthrange of 500 to 600 nm, 1-surface photopic average reflectance of 0.58%at normal incidence, 1-surface reflected b* within −21 to +5 over theentire range of viewing angles from 0 to 90 degrees, and 1-surfacereflected a* within 0 to +11.5 over the entire range of viewing anglesfrom 0 to 90 degrees.

Table 7 shows the structure of Example 1.

TABLE 7 Example 1, Structure Thickness Refractive Index Layer (nm) @550nm 5318 Glass Substrate 1.51 Linear Gradient 640 Graded from w/RI slope1.51 to 2.006 in of = +0.0008/nm steps of 20 nm AlO_(x)N_(y) 2000 2.006Linear Gradient 33 Graded from w/RI slope 2.006 to 1.481 in of =−0.0155/nm steps of 1 nm SiO2 78 1.481 Air Medium 1

Table 8 shows 1-side reflected color, 2-side transmitted color, photopicaverage reflectance, and photopic average transmittance for Example 1.

TABLE 8 Ex. 1, 1st-surface Reflectance Photopic Incident AverageReflected Reflected Angle (deg) % R (D65) a* (D65) b* (D65) 0 0.58 9.66−20.60 6 0.57 9.74 −20.38 10 0.56 9.89 −19.98 20 0.54 10.49 −17.86 300.61 11.34 −13.57 40 0.95 10.72 −6.46 50 2.03 7.54 0.97 60 5.03 4.744.29 70 13.24 2.73 4.29 80 35.87 1.21 2.63 90 100 0 0 Ex. 1, 2-surfaceTransmittance Photopic Incident Average Transmitted Transmitted Angle(deg) % T (D65) a* (D65) b* (D65) 0 95.40 −0.40 1.21 6 95.40 −0.40 1.1910 95.41 −0.41 1.15 20 95.40 −0.43 0.98 30 95.22 −0.46 0.73 40 94.53−0.49 0.40 50 92.51 −0.51 0.03 60 87.26 −0.50 −0.31 70 74.41 −0.43 −0.5480 46.29 −0.30 −0.51 90 0 0 0

FIG. 17 shows the coating design of Example 1 as a plot of RefractiveIndex vs. position. FIG. 18 shows detail fora part of the coating designof Example 1 as a plot of Refractive Index vs. position. FIG. 19 showsreflectance spectra for Example 1. FIG. 20 shows transmittance spectrafor Example 1. FIG. 21 shows a plot of surface reflected D65 color vs.angle for Example 1. FIG. 19 and FIG. 21 are based on incident lightpassing right to left in FIG. 17 . Example 1 exhibits a monotonicincrease in refractive index from the substrate up to a thick hardcoating layer, and a monotonic decrease in refractive index from thethick hard coating layer down to the external user surface.

Example 2

Example 2 comprises a hardcoated, chemically strengthened glass havingan anti-reflective top portion to the hardcoating. This anti-reflectivetop portion comprises a gradient layer that is 56 nm thick comprising agradual change in refractive index from 2.006 to 1.565 as furtherdetailed in above tables and figures, followed by a top-most ‘cap’ layerof 60 nm thickness having an index of 1.565 (e.g. a mixture of sputteredSiO₂ and AlO_(x)N_(y)). This 56 nm gradient layer and 60 nm cap layerfunction together to provide an optical-interference-basedanti-reflective effect, while also removing abrupt interfaces formechanical performance improvement. The terminal index of 1.565 allowsfor a boost in hardness at the outermost surface and a narrower colorrange, while sacrificing some of the lowest achievable reflectance.Example 2 has 1-surface reflectance below 2.0% for the entire range from520 to 620 nm wavelength, 1-surface reflected b* within −12 to +2 overthe entire range of viewing angles from 0 to 90 degrees, and 1-surfacereflected a* within 0 to +5 over the entire range of viewing angles from0 to 90 degrees.

Table 9 shows the structure of Example 2.

TABLE 9 Example 2, Structure Thickness Refractive Index Layer (nm) @550nm 5318 Glass Substrate 1.51 Linear Gradient 640 Graded from w/RI slope1.51 to 2.006 in of = +0.0008/nm steps of 20 nm AlOxNy 2000 2.006 LinearGradient 56 Graded from w/RI slope 2.006 to 1.565 in of = −0.0076/nmsteps of 2 nm Mixture 14% 60 1.565 (AlOxNy):86% (SiO2) Air Medium 1

Table 10 shows 1-side reflected color, 2-side transmitted color,photopic average reflectance, and photopic average transmittance forExample 2.

TABLE 10 Example 2, Reflected and Transmitted Color Ex. 2, 1st-surfaceReflectance Photopic Incident Average Reflected Reflected Angle (deg) %R (D65) a* (D65) b* (D65) 0 1.75 4.09 −11.68 6 1.74 4.14 −11.57 10 1.744.23 −11.36 20 1.73 4.58 −10.30 30 1.82 4.92 −8.26 40 2.21 4.85 −5.18 503.42 4.12 −1.73 60 6.68 2.96 0.64 70 15.23 1.80 1.35 80 37.84 0.79 0.9490 100 0 0 Ex. 2, 2-surface Transmittance Photopic Incident AverageTransmitted Transmitted Angle (deg) % T (D65) a* (D65) b* (D65) 0 94.32−0.28 1.03 6 94.32 −0.28 1.01 10 94.33 −0.29 0.99 20 94.31 −0.31 0.89 3094.13 −0.34 0.72 40 93.44 −0.37 0.50 50 91.43 −0.39 0.25 60 86.22 −0.390.00 70 73.53 −0.32 −0.17 80 45.76 −0.21 −0.20 90 0 0 0

FIG. 22 shows the coating design of Example 2 as a plot of RefractiveIndex vs. position. FIG. 23 shows detail for a part of the coatingdesign of Example 2 as a plot of Refractive Index vs. position. FIG. 24shows reflectance spectra for Example 2. FIG. 25 shows transmittancespectra for Example 2. FIG. 26 shows a plot of surface reflected D65color vs. angle for Example 2. FIG. 24 and FIG. 26 are based on incidentlight passing right to left in FIG. 22 . Example 2 exhibits a monotonicincrease in refractive index from the substrate up to a thick hardcoating layer, and a monotonic decrease in refractive index from thethick hard coating layer down to the external user surface.

Example 3

Example 3 comprises a hardcoated, chemically strengthened glass havingan anti-reflective top portion to the hardcoating. This anti-reflectivetop portion comprises a series of 4 gradient index layers and 3‘plateau’ index layers having a combined thickness (4 gradients plus 3plateaus) of 105 nm, followed by a top-most ‘cap’ layer of 65 nmthickness having an index of 1.481 (e.g. sputtered SiO₂), as furtherdetailed in above tables and figures. This multi-step gradient, plateau,and cap layer function together to provide an optical-interference-basedanti-reflective effect, while also removing abrupt interfaces formechanical performance improvement. The multi-step gradient and plateaustructure allows for flattening the reflectance spectrum and minimizingthe range of color shift with viewing angle. Example 3 has 1-surfacereflectance below 2.1% for the entire range from 420 to 720 nmwavelength, 1-surface reflected b* within −2 to +1 over the entire rangeof viewing angles from 0 to 90 degrees, and 1-surface reflected a*within −1 to +1 over the entire range of viewing angles from 0 to 90degrees.

Table 11 shows the structure of Example 3.

TABLE 11 Example 3, Structure Thickness Refractive Index Layer (nm) @550nm 5318 Glass Substrate 1.51  Linear Gradient 960 Graded from w/RI slope1.51 to 2.006 in of = +0.0005/nm steps of 30 nm AlOxNy 1200 2.006 LinearGradient 10.5 Graded from w/RI slope 2.006 to 1.898 in of = −0.0089/nmsteps of 1.5 nm Mixture 77% 37 1.898 (AlOxNy):23% (SiO2) Linear Gradient12 Graded from w/RI slope 1.898 to 1.763 in of = −0.0097/nm steps of 1.5nm Mixture 50% 18 1.763 (AlOxNy):50% (SiO2) Linear Gradient 10.5 Gradedfrom w/RI slope 1.763 to 1.634 in of = −0.0104/nm steps of 1.5 nmMixture 26% 5 1.634 (AlOxNy):74% (SiO2) Linear Gradient 12 Graded fromw/RI slope 1.634 to 1.481 in of = −0.0116/nm steps of 1.5 nm SiO2 651.481 Air Medium 1   

Table 12 shows 1-side reflected color, 2-side transmitted color,photopic average reflectance, and photopic average transmittance forExample 3.

TABLE 12 Ex. 3, 1st-surface Reflectance Photopic Incident AverageReflected Reflected Angle (deg) % R (D65) a* (D65) b* (D65) 0 1.80 −0.38−1.69 6 1.80 −0.39 −1.66 10 1.80 −0.41 −1.61 20 1.81 −0.44 −1.37 30 1.91−0.41 −1.03 40 2.25 −0.19 −0.65 50 3.30 0.21 −0.19 60 6.25 0.50 0.29 7014.34 0.55 0.61 80 36.61 0.39 0.56 90 100 0 0 0 1.80 −0.38 −1.69 6 1.80−0.39 −1.66 10 1.80 −0.41 −1.61 20 1.81 −0.44 −1.37 30 1.91 −0.41 −1.0340 2.25 −0.19 −0.65 50 3.30 0.21 −0.19 60 6.25 0.50 0.29 70 14.34 0.550.61 80 36.61 0.39 0.56 90 100 0 0

FIG. 27 shows the coating design of Example 3 as a plot of RefractiveIndex vs. position. FIG. 28 shows detail fora part of the coating designof Example 3 as a plot of Refractive Index vs. position. FIG. 29 showsreflectance spectra for Example 3. FIG. 30 shows transmittance spectrafor Example 3. FIG. 31 shows a plot of surface reflected D65 color vs.angle for Example 3. FIG. 29 and FIG. 31 are based on incident lightpassing right to left in FIG. 27 . Example 3 exhibits a monotonicincrease in refractive index from the substrate up to a thick hardcoating layer, and a monotonic decrease in refractive index from thethick hard coating layer down to the external user surface.

Example 4

Example 4 comprises a hardcoated, chemically strengthened glass havingan anti-reflective top portion to the hardcoating. This anti-reflectivetop portion comprises a series of 2 gradient index layers and 1‘plateau’ index layer having a combined thickness (2 gradients plus 1plateau) of 65 nm, followed by a top-most ‘cap’ layer of 65 nm thicknesshaving an index of 1.481 (e.g. sputtered SiO2), as further detailed inabove tables and figures. This multi-step gradient, plateau, and caplayer function together to provide an optical-interference-basedanti-reflective effect, while also removing abrupt interfaces formechanical performance improvement. Example 4 has 1-surface reflectancebelow 1.5% for the entire range from 525 to 625 nm wavelength, 1-surfacereflected b* within −10 to +2 over the entire range of viewing anglesfrom 0 to 90 degrees, and 1-surface reflected a* within 0 to +4 over theentire range of viewing angles from 0 to 90 degrees.

Table 13 shows the structure of Example 4.

TABLE 13 Example 4, Structure Thickness Refractive Index Layer (nm) @550nm 5318 Glass Substrate 1.51  Linear Gradient 640 Graded from w/RI slope1.51 to 2.006 in of = +0.0008/nm steps of 20 nm AlOxNy 2000 2.006 LinearGradient 14 Graded from w/RI slope 2.006 to 1.794 in of = −0.0142/nmsteps of 1 nm Mixture 56% 33 1.794 (AlOxNy):44% (SiO2) Linear Gradient18 Graded from w/RI slope 1.794 to 1.481 in of = −0.0165/nm steps of 1nm SiO2 65 1.481 Air Medium 1   

Table 14 shows 1-side reflected color, 2-side transmitted color,photopic average reflectance, and photopic average transmittance forExample 4.

TABLE 14 Ex. 4: 1st-surface Reflectance Photopic Incident AverageReflected Reflected Angle (deg) % R (D65) a* (D65) b* (D65) 0 1.36 1.63−9.16 6 1.35 1.70 −9.11 10 1.35 1.83 −9.01 20 1.34 2.40 −8.45 30 1.423.14 −7.11 40 1.76 3.64 −4.77 50 2.85 3.45 −1.75 60 5.90 2.71 0.56 7014.18 1.78 1.44 80 36.71 0.86 1.15 90 100 0 0 Ex. 4: 2-surfaceTransmittance Photopic Incident Average Transmitted Transmitted Angle(deg) % T (D65) a* (D65) b* (D65) 0 94.68 −0.09 0.69 6 94.68 −0.10 0.6810 94.69 −0.11 0.67 20 94.67 −0.14 0.63 30 94.50 −0.18 0.54 40 93.83−0.24 0.41 50 91.89 −0.29 0.23 60 86.76 −0.32 0.00 70 74.09 −0.31 −0.2380 46.17 −0.23 −0.35 90 0 0 0

FIG. 32 shows the coating design of Example 4 as a plot of RefractiveIndex vs. position. FIG. 33 shows detail for a part of the coatingdesign of Example 4 as a plot of Refractive Index vs. position. FIG. 34shows reflectance spectra for Example 4. FIG. 35 shows transmittancespectra for Example 4. FIG. 36 shows a plot of surface reflected D65color vs. angle for Example 4. FIG. 34 and FIG. 36 are based on incidentlight passing right to left in FIG. 32 . Example 4 exhibits a monotonicincrease in refractive index from the substrate up to a thick hardcoating layer, and a monotonic decrease in refractive index from thethick hard coating layer down to the external user surface.

Example 5

Example 5 comprises a hardcoated, chemically strengthened glass havingan anti-reflective top portion to the hardcoating. Example 5 comprises alow-reflectance hard coating with all gradient interfaces, averagephotopic visible reflectance <0.65%, 1-surface reflected b* within −8 to+4 over the entire range of viewing angles from 0 to 90 degrees, and1-surface reflected a* within 0 to +4 over the entire range of viewingangles from 0 to 90 degrees.

Table 15 shows the structure of Example 5.

TABLE 15 Example 5, Structure Thickness Refractive Index Layer (nm) @550nm 5318 Glass Substrate 1.51  Linear Gradient 990 Graded from w/RI slope1.51 to 2.006 in of = +0.0005/nm steps of 30 nm AlOxNy 980 2.006 LinearGradient 6 Graded from w/RI slope 2.006 to 1.955 in of = −0.0085/nmsteps of 2 nm Mixture 89% 64 1.955 (AlOxNy):11% (SiO2) Linear Gradient 6Graded from w/RI slope 1.955 to 2.006 in of = +0.0085/nm steps of 2 nmAlOxNy 110.7 2.006 Linear Gradient 34 Graded from w/RI slope 2.006 to1.481 in of = −0.0155/nm steps of 1 nm SiO2 72.7 1.481 Air Medium 1   

Table 16 shows 1-side reflected color, 2-side transmitted color,photopic average reflectance, and photopic average transmittance forExample 5.

TABLE 16 Ex. 5: 1st-surface Reflectance Photopic Incident AverageReflected Reflected Angle (deg) % R (D65) a* (D65) b* (D65) 0 0.64 3.05−7.60 6 0.64 2.96 −7.30 10 0.64 2.82 −6.78 20 0.66 2.33 −4.45 30 0.762.14 −1.12 40 1.13 2.48 2.17 50 2.22 2.95 3.59 60 5.25 2.98 3.59 7013.51 2.38 2.97 80 36.18 1.31 1.83 90 100 0 0 Ex. 5: 2-surfaceTransmittance Photopic Incident Average Transmitted Transmitted Angle(deg) % T (D65) a* (D65) b* (D65) 0 95.33 −0.13 0.41 6 95.33 −0.12 0.3910 95.33 −0.12 0.37 20 95.29 −0.10 0.26 30 95.09 −0.09 0.13 40 94.38−0.12 −0.01 50 92.37 −0.22 −0.14 60 87.13 −0.36 −0.28 70 74.29 −0.45−0.44 80 46.19 −0.40 −0.51 90 0.00 0.00 0.00

FIG. 37 shows the coating design of Example 5 as a plot of RefractiveIndex vs. position. FIG. 38 shows detail for a part of the coatingdesign of Example 5 as a plot of Refractive Index vs. position. FIG. 39shows reflectance spectra for Example 5. FIG. 40 shows transmittancespectra for Example 5. FIG. 41 shows a plot of surface reflected D65color vs. angle for Example 5. FIG. 39 and FIG. 41 are based on incidentlight passing right to left in FIG. 37 .

Example 5A

Example 5A comprises a coating design and refractive index profilenearly identical to example 5, but SiOxNy made in metal-mode reactivesputtering is used in the place of AlOxNy, and SiO₂ made by the samemethod, having a slightly different refractive index than that ofExample 5.

Table 17 shows the structure of Example 5A.

TABLE 17 Example 5A, Structure Thickness Refractive Index Layer (nm)@550 nm 5318 Glass Substrate 1.51  Linear Gradient 990 Graded from w/RIslope 1.51 to 2.007 in of = +0.0005/nm steps of 30 nm SiOxNy 980 2.007Linear Gradient 6 Graded from w/RI slope 2.007 to 1.955 in of =−0.0085/nm steps of 2 nm Mixture 90.2% 64 1.955 (SiOxNy):9.8% (SiO2-a)Linear Gradient 6 Graded from w/RI slope 1.955 to 2.007 in of =+0.0085/nm steps of 2 nm SiOxNy 110.7 2.007 Linear Gradient 34 Gradedfrom w/RI slope 2.007 to 1.476 in of = −0.0155/nm steps of 1 nm SiO2-a72.7 1.476 Air Medium 1   

Table 18 shows 1-side reflected color, 2-side transmitted color,photopic average reflectance, and photopic average transmittance forExample 5.

TABLE 18 Ex. 5A: 1st-surface Reflectance Photopic Incident AverageReflected Reflected Angle (deg) % R (D65) a* (D65) b* (D65) 0 0.599 3.05−7.18 6 0.599 2.97 −6.87 10 0.599 2.83 −6.33 20 0.62 2.36 −3.90 30 0.732.21 −0.59 40 1.10 2.64 2.72 50 2.19 3.09 3.98 60 5.21 3.08 3.85 7013.46 2.45 3.14 80 36.13 1.35 1.93 90 100 0 0 Ex. 5A: 2-surfaceTransmittance Photopic Incident Average Transmitted Transmitted Angle(deg) % T (D65) a* (D65) b* (D65) 0 95.19 −0.31 0.98 6 95.19 −0.31 0.9610 95.19 −0.30 0.94 20 95.15 −0.28 0.85 30 94.93 −0.28 0.73 40 94.21−0.33 0.61 50 92.20 −0.43 0.49 60 86.96 −0.57 0.35 70 74.14 −0.67 0.2080 46.07 −0.63 0.18 90 0 0 0

The coating design of Example 5A is similar to that illustrated in FIG.37 and FIG. 38 for Example 5. FIG. 42 shows reflectance spectra forExample 5A. FIG. 43 shows transmittance spectra for Example 5. FIG. 44shows a plot of surface reflected D65 color vs. angle for Example 5A.FIG. 42 and FIG. 44 are based on incident light passing right to left inFIG. 37 .

Example 6

Example 6 comprises a hardcoated, chemically strengthened glass, wherethe hardcoat is an all-gradient design. Example 6 was actuallyfabricated, and evaluated for hardness.

FIG. 48 shows the composition of the hardcoat of Example 6, in terms ofatomic concentration of different elements. Line 4810 shows elementalcarbon content. Line 4820 shows elemental nitrogen content. Line 4830shows elemental oxygen content. Line 4840 shows elemental aluminumcontent. Line 4850 shows elemental silicon content. Line 4860 showselemental potassium content.

FIG. 49 shows a refractive index profile for the hardcoat of Example 6.FIG. 49 was generated based on data measurement at limited pointsthrough the gradient, which confirm the intended refractive indexprofile that was used to determine the desired atomic concentration ofelements at various positions.

The highest absolute value of the slope of the refractive index inExample 6 was 0.0017/nm. The maximum hardness of the article of Example6 was measured to be 14.9 GPa. Example 6 demonstrates an all-gradienthardcoat having a high hardness.

It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thespirit or scope of the disclosure.

As used herein, the term “about” means that amounts, sizes,formulations, parameters, and other quantities and characteristics arenot and need not be exact, but may be approximate and/or larger orsmaller, as desired, reflecting tolerances, conversion factors, roundingoff, measurement error and the like, and other factors known to those ofskill in the art. When the term “about” is used in describing a value oran end-point of a range, the disclosure should be understood to includethe specific value or end-point referred to. Whether or not a numericalvalue or end-point of a range in the specification recites “about,” thenumerical value or end-point of a range is intended to include twoembodiments: one modified by “about,” and one not modified by “about.”It will be further understood that the endpoints of each of the rangesare significant both in relation to the other endpoint, andindependently of the other endpoint.

The terms “substantial,” “substantially,” and variations thereof as usedherein are intended to note that a described feature is equal orapproximately equal to a value or description. For example, a“substantially planar” surface is intended to denote a surface that isplanar or approximately planar. Moreover, “substantially” is intended todenote that two values are equal or approximately equal. In someembodiments, “substantially” may denote values within about 10% of eachother, such as within about 5% of each other, or within about 2% of eachother.

Directional terms as used herein—for example up, down, right, left,front, back, top, bottom—are made only with reference to the figures asdrawn and are not intended to imply absolute orientation.

As used herein, the transitional term “comprising”, which is synonymouswith “including,” “containing,” or “characterized by,” is inclusive oropen-ended and does not exclude additional, unrecited elements or methodsteps. The transitional phrase “consisting of” excludes any element,step, or ingredient not specified in the list following “consisting of.”The transitional phrase “consisting essentially of” limits scope tospecified materials or steps “and those that do not materially affectthe basic and novel characteristic(s)” set forth in the claims.

As used herein the terms “the,” “a,” or “an,” mean “at least one,” andshould not be limited to “only one” unless explicitly indicated to thecontrary. Thus, for example, reference to “a component” includesembodiments having two or more such components unless the contextclearly indicates otherwise.

1. An article, comprising: a glass-ceramic substrate; and an opticalcoating on the glass-ceramic substrate, the optical coating comprising ahigh hardness portion and a compositional gradient portion, wherein thecompositional gradient portion extends from the high hardness portion tothe glass-ceramic substrate.
 2. The article defined in claim 1, whereinthe optical coating further comprising an additional compositionalgradient portion, wherein the additional compositional gradient portiondisposed on the high hardness portion.
 3. The article defined in claim1, wherein an absolute value of a slope of the refractive index of thecompositional gradient portion is 0.1/nm or less everywhere along thethickness of the compositional gradient portion.
 4. The article definedin claim 1, wherein a difference between a maximum refractive index ofthe compositional gradient portion and a minimum refractive index of thecompositional gradient portion is 0.05 or greater.
 5. The coated articledefined in claim 1, wherein the high hardness portion comprisesSiO_(x)N_(y), and the compositional gradient portion comprising at leasttwo of Si, Al, N, and O.
 6. An article comprising: a substratecomprising a first major surface; and an optical coating disposed overthe first major surface, the optical coating comprising: a second majorsurface opposite the first major surface, a thickness in a directionnormal to the second major surface, and a first gradient portion,wherein: a refractive index of the optical coating varies along thethickness of the optical coating between the first major surface and thesecond major surface; a difference between a maximum refractive index ofthe first gradient portion and a minimum refractive index of the firstgradient portion is 0.05 or greater; an absolute value of a slope of therefractive index of the first gradient portion is 0.1/nm or lesseverywhere along the thickness of the first gradient portion; whereinthe article exhibits: a maximum hardness in the range from about 10 GPato about 30 GPa, wherein maximum hardness is measured on the secondmajor surface by indenting the second major surface with a Berkovichindenter to form an indent comprising an indentation depth of about 100nm or more from the surface of the second major surface; and wherein theoptical coating further comprises a high hardness portion, and thecumulative thickness of any parts of the optical coating between thehigh hardness portion and the second major surface comprising a RI of1.6 or less is 200 nm or less.
 7. The article of claim 6, wherein thearticle exhibits a photopic average transmittance of 80% or more,measured at the second major surface.
 8. The article of claim 6,wherein: everywhere along the thickness of the first gradient portion,the absolute value of the slope of the refractive index of the opticalcoating is 0.001/nm or greater.
 9. The article of claim 6, wherein: thethickness of the high hardness portion is 200 nm or more; the averageindex of refraction in the high hardness portion is 1.6 or more; and themaximum hardness of the high hardness portion is 10 GPa or more, whereinmaximum hardness is measured by indenting the thick high hardnessportion with a Berkovich indenter to form an indent comprising anindentation depth of about 100 nm or more.
 10. The article of claim 9,wherein for 95% or more of the thickness of the high hardness portion,the difference between the maximum refractive index of the high hardnessportion and the minimum refractive index of the high hardness portion is0.05 or less.
 11. The article of claim 9, wherein the optical coatingcomprises, in order, along the direction of the thickness from thesecond major surface toward the first major surface: the high hardnessportion; and the first gradient portion in contact with the highhardness portion; wherein, where the high hardness portion contacts thefirst gradient portion, the difference between the refractive index ofthe high hardness portion and the maximum refractive index of the firstgradient portion is 0.05 or less.
 12. The article of claim 9, whereinthe optical coating further comprises a second gradient portion disposedon the high hardness portion, wherein the second gradient portion is incontact with the high hardness portion, and wherein: the differencebetween the maximum refractive index of the second gradient portion andthe minimum refractive index of the second gradient portion is 0.05 orgreater; everywhere along the thickness of the second gradient portion,the absolute value of the slope of the refractive index of the opticalcoating is 0.1/nm or less.
 13. The article of claim 12, wherein: therefractive index of the first gradient portion monotonically increasesalong the thickness in a direction moving away from the second majorsurface; the refractive index of the second gradient portionmonotonically decreases along the thickness in a direction moving awayfrom the second major surface.
 14. The article of claim 12, wherein theoptical coating consists of the first gradient portion, the highhardness portion, and the second gradient portion, and wherein theoptical coating is in direct contact with the substrate, and wherein thesecond major surface is an outer surface.
 15. The article of claim 6,wherein everywhere in the optical coating, the absolute value of theslope of the refractive index of the optical coating is 0.1/nm or less.16. The article of claim 6, wherein the article exhibits a single sidereflected color range for all viewing angles from 0 to 60 degrees,measured at the second major surface, that comprises all a* and all b*points comprising absolute values of 20 or less.
 17. The article ofclaim 6, wherein optical coating comprises a thickness in the range fromabout 0.5 μm to about 3 μm.
 18. The article of claim 6, wherein theoptical coating comprises a compositional gradient, the compositionalgradient comprising at least two of Si, Al, N, and O.
 19. The article ofclaim 6, wherein the article exhibits a single side photopic averagelight reflectance of 3% or less, measured at the second major surface.20. The article of claim 6, wherein the slope is measured along thethickness over a refractive index change of 0.04.
 21. Glasses,comprising a lens, wherein the lens comprises an article according toclaim
 6. 22. A consumer electronic product, comprising: a housing havinga front surface, a back surface and side surfaces; electrical componentsdisposed at least partially within the housing, the electricalcomponents comprising at least a controller, a memory, and a display,the display at or adjacent the front surface of the housing; and a coversubstrate disposed over the display, wherein at least one of a portionof the housing or the cover substrate comprises the article of claim 6.23. A method of forming an article comprising: obtaining a substratecomprising a first major surface and comprising an amorphous substrateor a crystalline substrate; disposing an optical coating on the firstmajor surface, the optical coating comprising a second major surfaceopposite the first major surface and a thickness in a direction normalto the second major surface, creating a refractive index gradient alongat least a first gradient portion of the thickness of the opticalcoating, wherein: a refractive index of the optical coating varies alonga thickness of the optical coating between the first major surface andthe second major surface; the difference between the maximum refractiveindex of the first gradient portion and the minimum refractive index ofthe first gradient portion is 0.05 or greater; the absolute value of theslope of the refractive index of the first gradient portion is 0.1/nm orless everywhere along the thickness of the first gradient portion;wherein the article exhibits: a single side photopic average lightreflectance of 3% or less, measured at the second major surface, and amaximum hardness in the range from about 10 GPa to about 30 GPa, whereinmaximum hardness is measured on the second major surface by indentingthe second major surface with a Berkovich indenter to form an indentcomprising an indentation depth of about 100 nm or more from the surfaceof the second major surface.
 24. The method of claim 23, whereincreating a refractive index gradient comprises varying along thethickness of the optical coating at least one of the composition and theporosity of the optical coating.
 25. The method of claim 23, wherein theoptical coating is disposed on the first major surface by a physicalvapor deposition sputter process.